DATA COLLECTION SURVEY ON FLOOD …FLOOD MANAGEMENT PLAN IN METRO MANILA Final Report May, 2014 Japan International Cooperation Agency (JICA) Yachiyo Engineering Co., Ltd. GE JR 14-119

Department of Public Works and Highway The Republic of Philippines

DATA COLLECTION SURVEY ON FLOOD MANAGEMENT PLAN IN

METRO MANILA

Final Report

May, 2014

Japan International Cooperation Agency (JICA)

Yachiyo Engineering Co., Ltd. GE

JR

14-119

The Republic of the Philippines Data Collection Survey on Flood Management in Metro Manila

Final Report i

Study Area

Pasig -Marikina River Basin C.A=641km2

Laguna Lake Basin C.A=3,281km2 Lake Area: around900km2

Laguna Lake

★ △

St.Nino

Rosario Weir

Manila

Manggahan Floodway

Napindan Cannel


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PHOTOS

Manggahan Floodway and Densely Urbanized Area (2009)1

Landuse Change around Outlet of Manggahan Floodway 1

Flood Disaster in 2009 2 Rosario Weir 3

1 Preparatory Study for Pasig-Marikina River Channel Improvement Project (JICA) 2 Flood Disaster caused by Ondoy Typhoon in 2009 3 Post Evaluation Report on “the Project for Rehabilitation of the Flood Control Operation and Warning System

in Metro Manila”

Marikina River

Manggahan Floodway


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SYNOPSIS

1 INTRODUCTION (1) Background The Pasig-Marikina-San Juan River System, of which total catchment area is 621 km2, runs through the center of Metro Manila and flows out to the Manila Bay. Its Main tributaries, the San Juan River and Napindan River, join the main stream at about 9.9 km and 19.9 km upstream from the Pasig River mouth, respectively. The three largest waterways contribute largely to the flooding in the metropolis brought about by the riverbank overflow of floodwaters. Metro Manila, which encompasses 16 cities and 1 municipality having a total projected population of over 11.5 million in 2010, is the economic, political and cultural center of the Philippines.

The department of Public Works and Highways (DPWH) conducted an updated Master Plan (M/P) for flood control and drainage improvement in Metro Manila and a Feasibility Study (F/S) on the channel improvement of the Pasig-Marikina River from January 1988 to March 1990, under a technical assistance from the Japan International Cooperation Agency (JICA), called “The Study on Flood Control and Drainage Project in Metro Manila (JICA M/P Study)” and PMRCIP has been implemented based on the Master Plan.

On the other hand, the World Bank conducted the study “Master Plan for Flood Management in Metro Manila and Surrounding Areas” (“WB Study”) under the objective to establish the vision, which will be the blue print or road map, for a sustainable and effective flood risk management in Metro Manila and surrounding areas until 2035.

The WB Study has shown the results; 1) Review of current situation and arrangement of flood risk management, 2) Study on the mechanism of floods and flood damage, 3) Identification of constraints and barriers for flood risk management and directions for improvement, and 4) Formulation of the macro-framework for integrated flood risk management plan.

Based on the results of the WB Study and JICA M/P Study, JICA conducts “Data Collection Survey on Flood Management Plan in Metro Manila” to further examine with the detailed flood control measures in Pasig-Marikina River Basin.

(2) Objective and Study Items

The objective is to reexamine the technical validity of the proposed structural measures in Pasig-Marikina River Basin under the WB Study by utilizing the hydrological and hydrodynamic flood simulation model which is to be refined and updated with appropriately selected dataset in consideration of the future climate change. Main work items are 1) Collection and Utilization of Previous Study Results, 2) Establishment of Flood Analysis Model, 3) Analysis of Design High-water Discharge, 4) Analysis of Water Level Fluctuation in Laguna Lake during Flood in Pasig-Marikina River and 5) Analysis of Climate Change Effects. The counterpart agency is Department of Public Works and Highway (DPWH) of the Republic of Philippine. Study area is Pasig-Marikina River Basin and Laguna Lake Basin in Metro Manila.

2 ESTABLISHMENT OF FLOOD ANALYSIS MODEL (1) Establishment of Flood Analysis Model

Runoff Analysis Model was established using “Water and Energy Budget-based Distributed Hydrological Model” (WEB-DHM) which can describe spatial variations of basin such as topography, dynamic behavior of rainwater, soil characteristics, spatial variation of rainfall and so on.

Inundation Analysis Model is formulated by combining river hydraulic model utilizing one-dimensional unsteady flow analysis model with inundation model utilizing two-dimensional unsteady flow analysis model which can reproduce compound inundation phenomena of inland water and river flood, flow resistance due to land use and density of building, effects of channels, embankment, micro-topography, drainage and pump drainage and so on. Based on the survey conducted from December 2010 to January 2011, LiDAR data surveyed from December 2010 to


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January 2011 is utilized which is the newest and most accurate data.

(2) Calibration of Model with Past Floods Validity of established flood analysis model was calibrated comparing the observed discharge and water level data with simulation results such as discharge, river water level and inundation level.

Verification of H-Q Equations

Since the H-Q curves in previous studies (JICA MP and WB Study) have low reliability in high water level while the accuracies in low water level is high. Thus, the new H-Q curve which is recalculated by the Study are applied. Using the H-Q of this Study, the largest discharge in 2009 is estimated as 2,900m3/s.

Peak Water Level by Typhoon Ondoy at Sto.Nino Station

During the flood by Typhoon Ondoy, water level was not recorded at Sto.Nino Station after 18:00 on September 26 with the record of 22.16m, and the peak water level is uncertain. Based on the comparison of the peak discharges of past floods, the peak time of Sto.Nino during the flood by Typhoon Ondoy was estimated at 17:00 and water level is almost same as 22.16m which was observed at 18:00.

Selection of Past Floods for Model Calibration and Verification The 3 floods in Typhoon Ondoy in 2009, November 2004 and August 2008 were selected for calibration and verification of the flood analysis model as the 3 largest basin daily rainfalls were recorded.

Establishment of Flood Analysis Model

Model calibration was conducted as the following procedure.

Discharge to river course without inundation in upstream basin estimated by the runoff model (WEB-DHM) is given to the inundation model as a boundary condition.

Water level in river course and inundation area is estimated by the inundation model Parameters are evaluated comparing estimated discharge, water level and inundation area to the

observed ones.

The 2009 Flood (Typhoon Ondoy) was selected for calibration. The established model shows good reproductivity for relatively small peak flood such as the 2004 Flood and multi-peak flood such as 2012 Flood.

3 ANALYSIS OF DESIGN FLOOD DISCHARGE (1) Preconditions for Analysis

As preconditions for analysis of design flood discharge, existing facilities, plans f are confirmed.

Existing Facilities

Manggahan Floodway was constructed in 1988 to protect the center of Metro Manila from 100 years probable flood with design discharge of 2,400m3/s.

Currently, the original flow capacity has been reduced mainly due to illegal houses in the course of floodway and sedimentation.

Current Flow Capacity

The average ratio of current flow capacities against design discharges are about 50% in Pasig, 80% in lower Marikina and 20% in upper and upper-upper Marikina. Flood control ratio is especially low in upper and upper-upper Marikina.

Pasig-Marikina River Channel Improvement Project (Phase III) The objective of the overall project is to increase flood safety of Pasig-Marikina River to 1/30 years probable flood. The Phase III Project covers the sections which are not covered by the ongoing Phase II Project. Design discharges are set assuming MCGS will be constructed in the future. The design discharges are 2,900m3/s at Sto.Nito. It is diverted to Manggahan Floodway with 2,400m3/s and Lower


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Marikina with 500m3/s by MCGS at Rosario, and the river discharges increase to 600m3/s at upstream and to 1,200m3/s at downstream of Pasig River.

Proposed Projects by WB Study

The Proposed projects by the WB Study consists the improvement of Upper and Upper-Upper Marikina River, Marikina Large Dam, re-improvement of Pasig River and Lower Marikina River and improvement of San Juan River and Napindan Channel with design flood discharge of 1/100 years return period and the target year of 2035. In the WP Plan, the current diversion system using both Manggahan Floodway and Napindan Channel is applied without construction of MCGS. , which is against the concept of PMRCIP. The design discharge is 2,900m3/s at Sto.Nito by controlling by a Marikina large dam. It becomes 3,000m3/s at Rosario and is diverted to Manggahan Floodway with 2,000m3/s and Lower Marikina with 1,000m3/s and the design discharge of 1,200m3/s at NHCS is further diverted to Napindan Channel with 600m3/s, and the design discharge becomes 850m3/s at Upper Pasig and 1,800m3/s at Lower Pasig.

(2) Review of Rainfall Analysis Conditions for calculation and its results as 30 years and 100 years return periods rainfall which obtained by the Study of Water Security Master Plan for Metro Manila and its Adjoining Areas (hereinafter referred to as the JICA Water Security Study) are examined.

The JICA Water Security Study applied 1 day rainfall based on the analysis for correlation between rainfall duration and peak water level at Sto.Nino, while the previous studies applied 2 days rainfall.

Besides, the JICA Water Security Study applied several design hyetographs based on the observed hyetographs while the previous studies applied only milled-peak fictional hyetograph and the hyetograph of Typhoon Ondoy.

(3) Basic Design Discharge

Based on the established flood analysis model, basic design discharge is estimated using the hyetographs. The largest discharge at Sto.Nino is estimated using the hyetograph of Typhoon Ondoy of which discharges are 3,575m3/s with natural retarding function (inundation in upstream) and 4,980m3/s without inundation in upstream. Thus, the basic design discharge is determined using the hyetograph of Typhoon Ondoy. It is noted that probability 1 day rainfall of the hyetograph of Typhoon Ondoy is evaluated as 1/110 years, however, it is not cut down to meet the 1/100 years rainfall since the both values are almost same.

Water Level of Laguna Lake Since there is a possibility that the peak discharges at Marikina River and Laguna Lake occur at same time, the highest water level after 1989 when Manggahan Floodway constructed, 13.90m is applied in this Study. For water level rise of Laguna Lake in the case of Typhoon Ondoy, inflow from Manggahan Floodway and Napindan Channel contributes to 0.18m which is only 17% of total water level rise during the Typhoon Ondoy.

(4) Design Flood Discharge

Operation of NHCS With the following reasons, it is judged as appropriate that NHCS shall be closed during flood to avoid uncertain phenomena in flood management plan.

Diversion through Napindan Channel to Laguna Lake is uncertain since reverse flow will happen depending on water level in Laguna Lake.

If NHCS would open during flood, channel improvement of Napindan Channel is inevitable to protect surrounding dense urbanized area resulting difficulty of land acquisitions.

Necessity of MCGS

MCGS is necessary for sure diversion of design discharge to Laguna Lake. Besides, excess flood also can be diverted to Manggahan Floodway by MCGS resulting mitigation of flood risk at the center of Metro Manila.

Without MCGS, re-improvement of channel downstream of Rosario Weir since HWL increases. Rise


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of HWL leads to increase of flood disaster potentials.

Evaluation of Probability of Design Flood Discharge by PMRCIP PMRCIP is to divert the design discharge equivalent to 1/30 years probable flood at Sto.Nino of 2,900m3/s to Manggahan Floodway with 2,400m3/s and Pasig-Marikina River with 500m3/s. Based on the review of hydrological analysis referring the observed floods in recent years, the design flood discharge of PMRCIP of 2,900 m3/s is reevaluated as 1/20 years flood.

Alternatives of Flood Management Plan for 1/30 Flood As the urgent flood management measures until the completion of Phase IV Project, the following 3 alternatives are proposed.

Alt-O: 1/30 years flood (as of 2002) measures by Phase IV component (Q=2,900m3/s at Sto.Nino) Alt-A: 1/30 years flood measures by Phase IV components with improvement of Manggahan

Floodway (Q=3,100m3/s at Sto.Nino) Alt-B: 1/30 years flood measures by Phase IV components with improvement of retarding basin

in upper-upper Marikina (Q=2,900m3/s at Sto.Nino)

Flood Management Plan for 1/100 Years Flood

Based on the above mentioned 3 alternatives for 1/30 years flood management plan, 10 alternatives are proposed considering step-wise development.

Implementing “dam” or “dam + retarding basin” development after the Phase IV Project completed, flood safety degree can be increased up to 1/100 years without re-investment to the past developed section.

“Dam + Retarding Basin” options can increase safety degree by stages. “Dam” options can be taken if geological conditions in upstream basin is good enough. Since

retarding basin is not required or can be reduced after completion of dam, land use such as urban development is available.

Comparison with WB Proposal

The alternatives for 1/100 years flood and the WB proposed measures are compared and the following differences are found.

The WB proposal utilizes the current flood management system without MCGS by which step-wise improvement of flood safety is impossible.

It includes the uncertain function of natural diversion at NHCS which might not always occur. It requires large scale of dredging work in Lower Pasig River and it will be repeatedly conducted. Re-investment is required to PMRCIP such as heightening of dykes and replacement of bridges.

Investigation of Appropriateness of Measures to Floods The appropriateness of measures to floods is investigated by Economic Evaluation taking into consideration this project forms a part of the public investment in order to reduce floods damage in the Metro Manila. As shown in the table below, economic feasibility is confirmed for all alternatives.

It varies depending on the alternatives, however, EIRR exceeds 15% in all cases. In all cases, NPV is largely surplus the cost. It varies depending on the alternatives, however, B/C exceeds 1.00 in all cases.

4 WATER LEVEL FLUCTUATION IN LAGUNA LAKE DURING FLOOD IN PASIG-MARIKINA RIVER

In order to examine the validity of water level fluctuation of Laguna Lake, and the measure against floods, data collection and its arrangement are performed about flow regime of the water fluctuation data of Laguna Lake lake and both Manggahan Floodway and Napindan Channel during the floods, and the water level fluctuation analysis model of Laguna Lake is built based on the water level fluctuation characteristic of Laguna Lake as follows.

(1) Water Level Fluctuation of Laguna Lake


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Secular change of monthly variation of water level at Anogono Station from 1994 to 2012 is summarized. Water level of Laguna Lake becomes the lowest in April or May, which is the end of dry season, and becomes the highest in late rainy season in September to January. The average annual lowest and highest water levels are EL. 10.8m and EL. 12.4m, respectively. The average annual lowest water level is almost same as the mean sea level (MSL) of Manila Bay. It means that sea water intrusion to Laguna Lake occurs when high tide in the end of dry season.

For water level fluctuation during flood, hourly hydrograph in 2004 in which two floods were occurred by the tropical cyclone Wennie in August and the typhoon Yoyong in December is analyzed comparing the water levels among Rosario JS, Napindan JS and Laguna Lake. During flooding stage, water level of Rosario JS is more sensitive and always higher than Laguna Lake. It is expected that natural discharge to Laguna Lake through Manggahan Floodway always occurs during floods. On the other hand, clear correlation cannot be found between the water levels of Napindan JS and Laguna Lake. It is judged that natural diversion from Pasig River to Laguna Lake through Napindan Channel does not always occur.

(2) Water Level Fluctuation Model

Establishment of Analysis Model The long-term one dimensional model correlating the water level at Angono, inflow discharge from tributaries, inflow from Rosario JS, inflow through Manggahan Floodway, inflow and outflow through Napindan Channel, and evaporation from Lake surface is established and calibrated with observed data in 2004 and 2009.

Validity of Including reverse flow (Napindan Waterway) of Laguna in Flood Measure Plan Based on observed data in 2004 and analysis results in 2004 and 2009, water level of Rosario JS is always higher than Laguna Lake during floods. On the other hand, water level of Napindan JS is lower than Laguna Lake in many cases. Although it becomes higher than Laguna Lake occasionally depending of tidal level, its uncertainty is high to expect as flood control function and it is not recommended to include this phenomena as a flood control measure.

Influence of inflow from Pasig-Marikina River to Water Level Fluctuation of Laguna Lake

82 % of inflow to Languna Lake during Typhoon Ondoy is came from Laguna Lake Basin, while only 10 % comes through Manggahan Flood way and 8 % comes through Napindan Channel. Based on this simulation results, it is judged that influence of inflow from Pasig-Marikina River is very small to water level fluctuation of Laguna Lake.

Influence on Laguna Lake accompanying a Climate Change

Considering the climate change effect in 2040, 11.82 m of simulated high water level in 2004 becomes 11.93 m (+0.11 m) and 13.96 m of simulated high water level during Typhoon Ondoy invasion in 2009 becomes 14.25 m (+0.29 m).

(3) Examination Validity of Flood Management Measures Based on the aforementioned examination, validity of the proposed flood management measures in this Study which discussed in Chapter 4 is confirmed in the aspect of effect to the water level of Laguna Lake.

Include reverse flow (Napindan Channel) to Laguna Lake in a flood measure plan.

In Napindan JS, the water level may become higher than Laguna Lake in some cases. However, the uncertainty of the flood regulation from a relation with a tide level is high, and it is not recommended to consider as a flood management measure.

Factor of a Laguna Lake water level rise The factor of a water level rise of Laguna Lake can be judged from the comparison result of amount of flood discharge. It is that the rainfall to the inflow river and the surface of Laguna Lake occupies about 80%.


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5 CLIMATE CHANGE EFFECT (1) Change of Flood Safety Degree Rainfall will increase about 10% in 2040 as a climate change impact, and rise of water level in Laguna Lake is expected to 29 cm as maximum. Besides, it is estimated based on the 4th IPCC report that tide level in Manila Bay rises about 22 cm. Peak discharges increase about 17 % for 1/30 years flood and about 10 % for 1/100 years flood. Therefore, safety degree of 1/30 years decline to 1/20 years and 1/100 years decline to 1/60 years.

(2) Change of Inundation by Climate Change after Phase IV Project Completion

Inundation areas increase about 1.26 times for 1/30 years flood and about 1.12 times for 1/100 years flood. On the other hand, inundation depths decrease about 15 cm for 1/30 years flood and about 9 cm for 1/100 years flood due to spread of inundation areas induced by increase of discharges.

(3) Adaptation Measures against Climate Change The adaptation structural measures can be categorized into the measures upstream and downstream of MCGS.

The measures upstream of MCGS can be divided into the measures for flood control facilities upstream of Sto.Nino such as increase of capacities of retarding basins, improvement of flood control function of dam and additional dam and increase of diversion discharge to Laguna Lake such as increase of capacity of Manggahan Floodway by dredging or new floodway.

The measures downstream of MCGS is mainly the measures to reduce inflow discharge from San Juan River such as underground floodway, underground storage and runoff control facilities such as retarding storage, rainwater storage and infiltration facilities.

Non-structural measures shall be implemented according to change of inundation conditions induced by the climate change such as evacuation system improvement, hazard map and landuse regulation, and conservation of retarding function of basins.

6 CONCLUSION AND RECOMMENDATION The works in this Study can be broadly categorized into the followings.

(a) Establishment of hydrological and hydrodynamic flood simulation model with appropriately selected dataset in consideration of the future climate change

(b) Reevaluation of technical validity of the proposed structural measures in Pasig-Marikina River Basin under the WB Study

(c) Examination of flood management measures against 1/30 and 1/100 years probable floods and proposal of direction of flood management measures

(1) Conclusion The results and conclusions of above mentioned work categories are summarized as follows.

1) Establishment of Hydrological and Hydrodynamic Flood Simulation Model with Appropriately Selected Dataset in Consideration of Future Climate Change

Flood analysis model is established integrating runoff analysis model (WEB-DHM Model), river hydraulic model (one dimensional unsteady flow model) and inundation analysis model (two dimensional unsteady flow model). Since the detailed elevation data named LiDAR data, the latest river section survey, vegetation and landuse data, and timely and spatially varied hydrological data are utilized, accurate model against various types of flood including Typhoon Ondoy is established. Besides, H-Q equation is recalculated based on the detailed section data and discharges are estimated.

Flood Analysis Model

WEB-DHM Model is applied for runoff analysis since it can analyze hydrologic cycle among atmosphere, vegetation and soils with high accuracy reflecting the change of runoff pattern by changing of vegetation and landuse of a basin, and time and spatial variations of meteorology.

For river hydraulic model and inundation model, one-dimensional unsteady flow analysis model and


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two dimensional unsteady flow analysis model are applied, respectively, since effect of water level of Laguna Lake, effects of past and planned river improvement works, and effects of natural or artificial retarding basin can be properly reflected.

Verification of Model by Various Types of Floods The river basin includes the center of Metro Manila in the downstream reach, and the river improvement works have been implemented to secure the safety against 1/30 years probable floods with assuming various types of floods. For examination of flood management measures against 1/100 years probable flood as the future target, various patterns of hyetographs such as high intensity with short period rainfall and long period rainfall including Typhoon Ondoy are utilized for calibration and verification of the model to improve the reproducibility of model.

Estimation of Discharge by New H-Q Equation Observed water level and discharge date is required for calibration of model parameters. However, there is no recent observed discharge data. H-Q equations have been formulated by previous studies, however, accuracy of high water level is uncertain because there is no observed discharge data. Thus, H-Q equation is re-formulated by non-uniform flow calculation based on the river section data combining LiDAR data and latest survey data, and detailed parameters.

2) Reevaluation of Technical Validity of Proposed Structural Measures in Pasig-Marikina River Basin under the WB Study

Design discharges of PMRCIP based on the JICA Master Plan in 1990 and the WB Study are shown in Figure 7.1.

PMRCIP proposed diversion to Lower Marikina with 500m3/s controlling by MCGS and shut down of NHCS during flood. On the other hand, the WB proposed that the diversion to Manggahan Floodway was controlled by Rosario Weir only without construction of MCGS, and natural diversion to Napindan Channel with NHCS open was expected.

Based on the analysis utilizing the established flood analysis model with referring the rainfall analysis results conducted by “the Study of Water Security Master Plan for Metro Manila and its Adjoining Areas” and the results of water level fluctuation analysis of Laguna Lake by this Study, technical validity of these proposals are reevaluated as follows.

Necessity of MCGS Diversion Function

The Study concludes that the proposed flood management measures by the Study including the MCGS function based on the JICA Master Plan is more effective than flood management measures without MCGS, in aspects of reliability, feasibility and step-wise improvement of flood safety. The features of flood management measures with MCGS are as follows.

<Reliability>

Various types of flood discharges can be securely diverted though Manggahan Flood way by the function of MCGS. As the results, Laguna Lake can be fully utilized as flood control facilities, and flood risk in lower reach can be reduced by controlling flood discharge to the downstream. This flood risk reduction in lower reach also works against excess floods or climate change impacts.

<Feasibility>

The flood management measures with MCGS function is more feasible since it does not reinvestment to the river sections where the river improvement works has been already implemented such as re-improvement of PMRCIP, reconstruction of existing bridges and re-improvement of Napindan Channel.

<Step-wise Improvement of Flood Safety>

With MCGS, the flood control works can be implemented separately by the upstream and downstream of MCGS since the discharge to downstream can be regulated by MCGS. Thus, improvement works can be implement in upstream sections with maintaining the safety against 1/30 years probable floods in the downstream of MCGS.

Besides, during the course of improvement of each section such as Lower Marikina and Upper-upper


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Marikina, flood safety can be improved step-wise without temporary decrease of flood safety of the Basin.

Operation of NHCS

The water level fluctuation analysis in Laguna Lake reveals that the water level at the inlet of Manggahan Floodway (Rosario Weir) is always higher than Laguna Lake while there is no clear correlation between the water levels at the confluence of Napindan Channel and Pasig River (NHCS) and Laguna Lake. It is also founded that impact of inflow discharge from Pasig-Marikina River to water level fluctuation in Laguna Lake is small. Thus, it is concluded that NHCS shall be closed during floods to mitigate increase of flood risk in Pasig-Lower Marikina Basin by preventing discharge from Laguna Lake to Pasig River.

By closing NHCS, discharge from Laguna Lake to Pasig River is blocked in case the water level of lake is higher than the river, resulting uncertainty of flood management is eliminated.

In case of natural diversion from Pasig River to Laguna Lake is expected in the flood management plan by opening NHCS, uncertainty of the plan remains since diversion will not occur if the water level of lake is higher than the river. Besides, there are many issues in this option such as a possibility to increase of flood risk in Pasig-Lower Marikina Basin against excess floods, necessity of reinvestment in PMRCIP (Phase II) section, large scale dredging and re-improvement of Napindan Channel which requires large scale land acquisition.

Dredging of Pasig River Under the alternative “Without MCGS and NHCS opening”, design discharge in Pasig River becomes 1,800m3/s which is about 1.5 times of the design discharge by PMRCIP of 1,200m3/s. To flow this discharge large scale dredging is required to deepen the riverbed about 2 to 3 m below the design riverbed in the master plan. Tremendous amount of maintenance cost is also required to maintain the riverbed.

In this Study, design discharge with 1/100 years return period becomes 1,400m3/s which is 200m3/s increase than the previous plan. However, it is within the flow capacity of channel if the riverbed is dredged until the design riverbed level. And scale of dredging works is also small which can be treated as a river maintenance works.

3) Flood Management Measures for 1/30 and 1/100 Years Probable Floods

Review of hydrology with the latest data, 1/30 years probable flood discharge is estimated at 3,100m3/s at Sto.Nino which is larger than the design discharge of PMRCIP at 2,900m3/s. As alternatives for 1/30 years probable flood management, 2 alternatives are proposed as well as the PMRCIP plan (Alt-O: Phase IV only), one is enhancement of Manggahan Floodway (Alt-A: Phase IV + Manggahan Floodway) and the other is enhancement of retarding basin (Alt-B: Phase IV + Retarding Basin). And combining “dam” or “dam + retarding basin” options, 10 alternatives for 1/100 years probable flood management are also proposed with step-wise development scenarios from 1/30 probable flood management measures, consisting of 4 alternatives from Alt-A, 2 alternatives from Alt-O and 4 alternatives from Alt-B. (Refer to Figure 7.2) Economic feasibility is confirmed for all alternatives. By applying one of these alternatives, the flood management in Pasig-Marikina River can adapt to impacts of climate change with various options.

(2) Recommendations

Necessity of Further Studies

This Study is conducted using the various data and information from the previous studies. Thus, it is recommended to conduct further investigations, studies and designs such as follows.

Optimal Location and Scale of Dam Scale and Capacity of Retarding Basin, Area of Natural Retarding Basin Design Flood Discharge in Phase IV Section and HWL Area of Channel Excavation of Manggahan Floodway

Restoration and Improvement of Manggahan Floodway

Manggahan Flood way was completed in 1988 with the design discharge of 2,400m3/s. However, flow


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area has been reduced mainly due to houses in river course and sedimentation. To divert flood discharge to Manggahan Floodway by MCGS, restoration of its function is a precondition. Resettlement and dredging shall be implemented to restore the original capacity.

In case of the design discharge at Sto.Nino is 3,100m3/s, flow capacity of Manggahan Floodway shall be increased to 2,600m3/s with additional 200m3/s. Considering excess floods and climate change impacts, capacity improvement of Manggahan Floodway is required. Enlargement of flow capacity of Manggahan Floodway by excavation is relatively easy since earth dyke is applied from Laguna Lake to 5km point.

Retention of Natural Retarding Function and Necessity of Detailed Investigation of Retarding Basin

The alternatives for 1/100 years probable flood management measures can be divided into “dam” options and “dam + retarding basin” options. Even if a “dam” option is selected, the current natural retarding function shall be maintained since the dam project needs long time. It is needed to fix the area of natural retarding basin and to regulate land use to maintain the natural retarding function.


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TABLE OF CONTENTS

STUDY AREA PHOTOS TABLE OF CONTENTS LIST OF FIGURES LIST OF TABLES ABBREVIATION・UNIT・LIST OF SOURCE

CHAPTER 1 INTRODUCTION ..................................................................................................... 1-1 1.1 Background and Objective of Study .......................................................................................... 1-1

1.1.1 Background ................................................................................................................... 1-1 1.1.2 Objective ....................................................................................................................... 1-2

1.2 Study Framework ....................................................................................................................... 1-2 1.2.1 Study Area ..................................................................................................................... 1-2 1.2.2 Summary of Study Purposes, Outputs and Activities ................................................... 1-2 1.2.3 Counterpart Agency by Philippines Side ...................................................................... 1-3

1.3 Schedule of Study ...................................................................................................................... 1-3 CHAPTER 2 CONDITIONS OF BASIN........................................................................................ 2-1 2.1 Natural Conditions of Basin ...................................................................................................... 2-1

2.1.1 Topography and Geology .............................................................................................. 2-1 2.1.2 Climate .......................................................................................................................... 2-1 2.1.3 Land Use Conditions ..................................................................................................... 2-2 2.1.4 Social Economy Conditions .......................................................................................... 2-3

2.2 River Conditions ........................................................................................................................ 2-6 2.2.1 Pasig River .................................................................................................................... 2-6 2.2.2 Marikina River .............................................................................................................. 2-6

2.3 Major Flood Disasters ................................................................................................................ 2-7 CHAPTER 3 ESTABLISHMENT OF FLOOD ANALYSIS MODEL .......................................... 3-1 3.1 Establishment of Flood Analysis Model ............................................................................................ 3-1

3.1.1 Runoff Analysis Model (WEB-DHM) ................................................................................. 3-1 3.1.2 Inundation Model ................................................................................................................. 3-3

3.2 Calibration of Model with Past Floods ............................................................................................ 3-14 3.2.1 Verification of H-Q Equations ........................................................................................... 3-14 3.2.2 Peak Water Level by Typhoon Ondoy at Sto.Nino Station ................................................ 3-18 3.2.3 Selection of Past Floods for Model Calibration and Verification....................................... 3-21

CHAPTER 4 ANALYSIS OF DESIGN FLOOD DISCHARGE ................................................... 4-1 4.1 Preconditions for Analysis ................................................................................................................. 4-1

4.1.1 Existing Facilities ................................................................................................................. 4-1 4.1.2 Current Flow Capacity ......................................................................................................... 4-2 4.1.3 Proposed Projects by Study on Flood Control and Drainage Project in Metro Manila........ 4-7 4.1.4 Pasig-Marikina River Channel Improvement Project (Phase III) ........................................ 4-8 4.1.5 Proposed Projects by WB Study ........................................................................................ 4-10 4.1.6 Comparison of Previous Studies ........................................................................................ 4-14

4.2 Review of Rainfall Analysis ............................................................................................................ 4-16 4.2.1 Results of Rainfall Analysis ............................................................................................... 4-16 4.2.2 Design Rainfall Duration ................................................................................................... 4-20 4.2.3 Basin Average Rainfall ....................................................................................................... 4-20 4.2.4 Basin Average Probable Rainfall ....................................................................................... 4-20

4.3 Basic Design Discharge ................................................................................................................... 4-21 4.3.1 Water Level of Laguna Lake .............................................................................................. 4-21 4.3.2 Basic Design Discharge ..................................................................................................... 4-23


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4.4 Design Flood Discharge .................................................................................................................. 4-30 4.4.1 Evaluation of Conditions for Pasig-Marikina River Channel Improvement Project

(PMRCIP) .......................................................................................................................... 4-30 4.4.2 Flood Management Plan for 1/30 Years Flood ................................................................... 4-35 4.4.3 Flood Control Measures for 1/100 Years Flood ................................................................. 4-49 4.4.4 Flood Management Plan for 1/100 Years Flood ................................................................. 4-58 4.4.5 Project Cost Estimate for Alternatives ............................................................................... 4-67

4.5 Investigation of Appropriateness of Measures to Floods ................................................................ 4-75 4.5.1 Economic Cost ................................................................................................................... 4-75 4.5.2 Economic Benefit ............................................................................................................... 4-76 4.5.3 Economic Evaluation ......................................................................................................... 4-82

4.6 Comparison of Study Contents and Results with Previous Studies ................................................. 4-83 CHAPTER 5 WATER LEVEL FLUCTUATION IN LAGUNA LAKE DURING FLOOD IN PASIG-MARIKINA RIVER ............................................................................................................... 5-1 5.1 Characteristics of Water Level Fluctuation of Laguna Lake ............................................................. 5-1

5.1.1 Available Data ...................................................................................................................... 5-1 5.1.2 Monthly Fluctuation of Water Level .................................................................................... 5-3 5.1.3 Water Level Fluctuation during Floods ................................................................................ 5-3

5.2 Water Level Fluctuation Model ......................................................................................................... 5-6 5.3 Examination Validity of Flood Management Measures .................................................................. 5-19 5.4 Remarks on Effect of Global Warming ........................................................................................... 5-19 CHAPTER 6 CLIMATE CHANGE EFFECT ................................................................................ 6-1 6.1 Change of Flood Safety Degree......................................................................................................... 6-1 6.2 Change of Inundation by Climate Change after Phase IV Project Completion ................................. 6-2 6.3 Adaptation Measures against Climate Change .................................................................................. 6-7

6.3.1 Structural Measures.............................................................................................................. 6-7 6.3.2 Non-Structural Measures ..................................................................................................... 6-9

CHAPTER 7 CONCLUSION AND RECOMMENDATION ........................................................ 7-1 7.1 Conclusion ......................................................................................................................................... 7-1

7.1.1 Establishment of Hydrological and Hydrodynamic Flood Simulation Model with Appropriately Selected Dataset in Consideration of Future Climate Change ...................... 7-1

7.1.2 Reevaluation of Technical Validity of Proposed Structural Measures in Pasig-Marikina River Basin under the WB Study ................................................................................................... 7-1

7.1.3 Flood Management Measures for 1/30 and 1/100 Years Probable Floods ........................... 7-3 7.2 Recommendations ............................................................................................................................. 7-4

7.2.1 Necessity of Further Studies ................................................................................................ 7-4 7.2.2 Restoration and Improvement of Manggahan Floodway ..................................................... 7-4 7.2.3 Retention of Natural Retarding Function and Necessity of Detailed Investigation of

Retarding Basin .................................................................................................................... 7-4

APPENDIX APPENDIX I: Figure APPENDIX II: Table APPENDIX III: Technical Working Group Material (September 6, 2013) APPENDIX IV: Explanatory Material to Secretary (February 13, 2014)


Final Report - 3 -

LIST OF FIGURES

Figure 2.1 Average Monthly Rainfall, Average Minimum and Maximum Temperatures in Metro Manila .......................................................................................................................................... 2-1

Figure 2.2 Land Use of Pasig-Marikina River Basin (as of 2005) ....................................................... 2-2 Figure 3.1 Outline of WEB-DHM Model ............................................................................................ 3-1 Figure 3.2 Area for Modeling............................................................................................................... 3-2 Figure 3.3 Basin Segmentation for Modeling ...................................................................................... 3-2 Figure 3.4 Outline of River Hydraulic Model and Inundation Analysis Model ................................... 3-4 Figure 3.5 Target Area for Inundation Analysis ................................................................................... 3-5 Figure 3.6 Cross Sections for Setup of Target Area (1/4) .................................................................... 3-6 Figure 3.7 Cross Sections for Setup of Target Area (2/4) .................................................................... 3-7 Figure 3.8 Cross Sections for Setup of Target Area (3/4) .................................................................... 3-8 Figure 3.9 Cross Sections for Setup of Target Area (4/4) .................................................................... 3-9 Figure 3.10 DEM Data Frameworks .................................................................................................. 3-10 Figure 3.11 100m x 100m Mesh Elevation ........................................................................................ 3-11 Figure 3.12 Floodplain Model............................................................................................................ 3-13 Figure 3.13 H-Q Curve Formulated in JICA M/P Study .................................................................... 3-14 Figure 3.14 H-Q Curve Formulated in WB Study ............................................................................. 3-15 Figure 3.15 Cross Section of Sto.Nino Station .................................................................................. 3-16 Figure 3.16 Sto.Nino Bridge .............................................................................................................. 3-16 Figure 3.17 Upstream of Sto.Nino Bridge ......................................................................................... 3-16 Figure 3.18 Recalculated H-Q Curve ................................................................................................. 3-17 Figure 3.19 Hydrograph of 2000 Flood ............................................................................................. 3-19 Figure 3.20 Hydrograph of 2004 Flood ............................................................................................. 3-19 Figure 3.21 Hydrograph of 2009 Flood ............................................................................................. 3-20 Figure 3.22 Hydrograph of 2011 Flood ............................................................................................. 3-20 Figure 3.23 Hydrograph of 2012 Flood ............................................................................................. 3-20 Figure 3.24 Hydrograph of Past Measure Floods .............................................................................. 3-22 Figure 3.25 Observed Inundation Map for 2009 Flood ..................................................................... 3-23 Figure 3.26 Observed and Calculated Hydrographs by WEB-DHM Model (2009 Flood at Sto.Nino)

.................................................................................................................................................... 3-24 Figure 3.27 Observed and Calculated Hydrographs by Inundation Model (2009 Flood) .................. 3-25 Figure 3.28 Observed and Calculated Hydrographs by Inundation Model (2009 Flood) .................. 3-26 Figure 3.29 Simulated Peak Discharge of 2009 Flood ....................................................................... 3-27 Figure 3.30 Observed and Calculated Hydrographs by WEB-DHM Model (2004 Flood) ................ 3-27 Figure 3.31 Observed and Calculated Hydrographs by Inundation Model (2004 Flood) .................. 3-28 Figure 3.32 Observed and Calculated Hydrographs by Inundation Model (2004 Flood) .................. 3-29 Figure 3.33 Observed and Calculated Hydrographs by WEB-DHM Model (2012 Flood) ................ 3-30 Figure 3.34 Observed and Calculated Hydrographs by Inundation Model (2012 Flood) .................. 3-31 Figure 3.35 Observed and Calculated Hydrographs by Inundation Model (2012 Flood) .................. 3-32 Figure 3.36 Inundation Simulation Results ........................................................................................ 3-33 Figure 4.1 Front View of Rosario Weir ................................................................................................ 4-1 Figure 4.2 Operation Rule of Rosario Weir ......................................................................................... 4-2 Figure 4.3 Current Flow Capacity (Pasig-Marikina River) .................................................................. 4-3 Figure 4.4 Current Flow Capacity (Pasig River).................................................................................. 4-4 Figure 4.5 Current Flow Capacity (Lower and Upper Marikina) ........................................................ 4-5 Figure 4.6 Current Flow Capacity (Upper-Upper Marikina River) ..................................................... 4-6 Figure 4.7 Proposed Projects and Design Discharge Allocation by JICA M/P Study .......................... 4-7 Figure 4.8 Design Flood Discharge Allocation for Phase III Project ................................................... 4-8 Figure 4.9 Proposed Projects by WB Study ....................................................................................... 4-11 Figure 4.10 Alternatives for Design Flood Discharge Allocation ...................................................... 4-12 Figure 4.11 Alternative Plans by WB Study ...................................................................................... 4-13 Figure 4.12 Design Hyetographs (1/100) (1/2) .................................................................................. 4-18 Figure 4.13 Design Hyetographs (1/100) (2/2) .................................................................................. 4-19 Figure 4.14 Correlation between Basin Average Rainfalls and Peak Discharge (Left: 1 day, Right: 2


Final Report - 4 -

days) ........................................................................................................................................... 4-20 Figure 4.15 H-V Curve of Laguna Lake ............................................................................................ 4-23 Figure 4.16 Factors of Water Level Rise in Laguna Lake during Typhoon Ondoy ........................... 4-23 Figure 4.17 Basic Design Discharge Allocation (Without Natural Retarding Function) ................... 4-24 Figure 4.18 Basic Design Discharge Allocation (With Natural Retarding Function) ........................ 4-25 Figure 4.19 Hyetograph and Hydrograph of 2009/9/26 Flood ........................................................... 4-26 Figure 4.20 Hyetograph and Hydrograph of 1998/10/22 Flood ......................................................... 4-26 Figure 4.21 Hyetograph and Hydrograph of 2004/11/29 Flood ......................................................... 4-27 Figure 4.22 Hyetograph and Hydrograph of 2003/5/27 Flood ........................................................... 4-27 Figure 4.23 Hyetograph and Hydrograph of 2000/7/7 Flood ............................................................. 4-28 Figure 4.24 Hyetograph and Hydrograph of 2011/6/24 Flood ........................................................... 4-28 Figure 4.25 Hyetograph and Hydrograph of 2000/11/2 Flood ........................................................... 4-29 Figure 4.26 Hyetograph and Hydrograph of Middle-peak Fictional Flood ....................................... 4-29 Figure 4.27 H-Q Curve Formulated in JICA M/P Study .................................................................... 4-30 Figure 4.28 Discharge Allocation With/Without MCGS (1/20 years, with Natural Retarding

Function) .................................................................................................................................... 4-32 Figure 4.29 Flow Profile With/Without MCGS ................................................................................. 4-33 Figure 4.30 H-Q Curve Formulated in WB Study ............................................................................. 4-34 Figure 4.31 Flow Profile of Influence of Urban Development Program ........................................... 4-34 Figure 4.32 Discharge Allocation of 1/30 Years Flood ...................................................................... 4-35 Figure 4.33 Alternative-a: Phase IV with Dyke Heightening + Improvement of Manggahan Floodway

(1/30 Years) ................................................................................................................................ 4-36 Figure 4.34 Alternative-b: Phase IV without Dyke Heightening + Construction of Retarding Basin

(1/30 Years) ................................................................................................................................ 4-37 Figure 4.35 Hydrograph at Sto.Nino before and after Control by Retarding Basin ........................... 4-38 Figure 4.36 Location of Natural Retarding Basin (Estimated Inundation Area of 1/30 years Flood)

.................................................................................................................................................... 4-39 Figure 4.37 Alternatives of Design Flood Discharge Allocation for 1/30 Years Flood ...................... 4-40 Figure 4.38 Flow Profile of Alternative-a .......................................................................................... 4-42 Figure 4.39 Flow Profile of Alternative-b .......................................................................................... 4-43 Figure 4.40 Current Conditions of Manggahan Floodway ................................................................ 4-44 Figure 4.41 Longitudinal Flow Profile (Current and after Excavation, Q=2,400m3/s) ...................... 4-44 Figure 4.42 Typical Section after Dredging Works ............................................................................ 4-45 Figure 4.43 Longitudinal Flow Profile (After Excavation, Q=2,400m3/s) ........................................ 4-45 Figure 4.44 Typical Section after Widening ....................................................................................... 4-46 Figure 4.45 Longitudinal Flow Profile (After Excavation Q=2,400m3/s, With Widening Q=2,600m3/s)

.................................................................................................................................................... 4-46 Figure 4.46 1/30 Years Flood Allocation in Pasig River .................................................................... 4-47 Figure 4.47 Hydrograph of 1/30 Years Flood at Confluence of San Juan River ................................ 4-47 Figure 4.48 Longitudinal Flow Profile of Pasig-Lower Marikina (Q=1,300m3/s) ............................ 4-48 Figure 4.49 Possible Flood Control Facilities Upstream of Sto.Nino for 1/100 Years Flood ............ 4-49 Figure 4.50 H-V Curve of Proposed Dam .......................................................................................... 4-50 Figure 4.51 Hydrographs at Dam Location ........................................................................................ 4-51 Figure 4.52 Hydrographs at Montalban ............................................................................................. 4-51 Figure 4.53 Hydrographs at Sto.Nino ................................................................................................ 4-52 Figure 4.54 Locations of Candidate Retarding Basin ........................................................................ 4-53 Figure 4.55 Hydrograph of Retarding Basin Effect at Sto.Nino (1/100 Flood) ................................. 4-54 Figure 4.56 Hydrographs of Dam + Retarding Basin Effect at Sto.Nino .......................................... 4-55 Figure 4.57 1/100 Years Flood Allocation in Pasig River and Hydrograph at Confluence of San Juan

River ........................................................................................................................................... 4-56 Figure 4.58 Longitudinal Flow Profile of Pasig-Lower Marikina (Q=1,400m3/s) ............................ 4-57 Figure 4.59 Pattern of Retarding Basin Development ....................................................................... 4-59 Figure 4.60 Alternatives of Phased Development Scenario ............................................................... 4-60 Figure 4.61 Images of Development Scenario(A-1 to A-3) ............................................................... 4-61 Figure 4.62 Images of Development Scenario(B-1 to B-4) ............................................................... 4-62 Figure 4.63 Map of areas likely to be inundated by probability year（1/2、1/5） .......................... 4-80


Final Report - 5 -

Figure 4.64 Map of areas likely to be inundated by probability year（1/10、1/20） ...................... 4-80 Figure 4.65 Map of areas likely to be inundated by probability year（1/30、1/50） ...................... 4-81 Figure 4.66 Map of areas likely to be inundated by probability year（1/100） ............................... 4-81 Figure 5.1 Locations of Rainfall Gauging Stations .............................................................................. 5-2 Figure 5.2 Locations of Water Level Gauging Stations ....................................................................... 5-2 Figure 5.3 Monthly Variation of Water Level in Laguna Lake ............................................................ 5-3 Figure 5.4 Hourly Hydrograph of Rosario JS and Angono (2004) ...................................................... 5-4 Figure 5.5 Comparison of Hourly Hydrograph Between Napindan JS and Angono (2004) ................ 5-4 Figure 5.6 Comparison of Daily Mean Hydrograph between Rosario JS and Angono (2004) ............ 5-5 Figure 5.7 Comparison of Daily Mean Hydrograph Between Napindan JS and Angono (2004) ........ 5-5 Figure5.8 Conceptual Figure of Water Level Fluctuation Analysis Model in Laguna Lake ................ 5-6 Figure5.9 Laguna Lake H-V Curve ..................................................................................................... 5-7 Figure 5.10 Applied Cross-sectional Properties ................................................................................... 5-8 Figure-5.11(1) Results of Laguna Lake Water Level Simulation (case of 2004 year) ....................... 5-10 Figure-5.11(2) Results of Laguna Lake Water Level Simulation (case of 2009 year) ....................... 5-11 Figure5.12 Best Track of Ondoy typhoon (T2009-16) ...................................................................... 5-11 Figure5.13 Best Track of Pepeng Typhoon (T2009-17) ..................................................................... 5-11 Figure 5.14 Water Level Fluctuation during Typhoon Ondoy Typhoon and Typhoon Pepeng ....... 5-12 Figure 5.15 Forecast Scenarios in IPCC 4th Assessment Report ....................................................... 5-14 Figure 5.16 Relation between Amount of Temperature Rises by Earth Models, and Amount of

Temperature Rises in Philippines ............................................................................................... 5-16 Figure 5.17 Amount of Temperature rises, and Relation of Rainfall Rate of Increase ...................... 5-16 Figure 5.18 Relation between the monthly temperature in Manila, and an amount of evaporation

(Makkink method) ...................................................................................................................... 5-17 Figure 5.19 (1) Result of Laguna Lake Water Level Analysis (2004 Year, Climate Condition in 2040

Year) ........................................................................................................................................... 5-18 Figure 5.19 (2) Result of Laguna Lake Water Level Analysis (2009 Year, Climate Condition in 2040

Year) ........................................................................................................................................... 5-18 Figure 6.1 Relation between Probability and Peak Discharge ............................................................. 6-2 Figure 6.2 Inundation Area by 1/30 Years Flood Without Climate Change Effect .............................. 6-3 Figure 6.3 Inundation Area by 1/30 Years Flood With Climate Change Effect ................................... 6-4 Figure 6.4 Inundation Area by 1/100 Years Flood Without Climate Change Effect ............................ 6-5 Figure 6.5 Inundation Area by 1/100 Years Flood With Climate Change Effect ................................. 6-6 Figure 6.6 Possible Structural Adaptation Measures ........................................................................... 6-7 Figure 6.7 Possible Non-Structural Adaptation Measures ................................................................. 6-10 Figure 7.1 Design Discharge of PMRCIP and the WB Study .............................................................. 7-1 Figure 7.2 Alternatives and Phased Development Scenarios ............................................................... 7-3


Final Report - 6 -

LIST OF TABLES

Table 1.1 Schedule of Study ................................................................................................................. 1-3 Table 2.1 Area of Relevant Governance Zones .................................................................................... 2-3 Table 2.2 Population of Relevant Governance Zones .......................................................................... 2-3 Table 2.3 Basic Economic Indicator of Philippines ............................................................................. 2-4 Table 2.4 Changes in Urbanization of NCR (1938 – 1994) ................................................................. 2-4 Table 2.5 Priority Industrial Clusters (2011 – 2016) ............................................................................ 2-6 Table 2.6 Major Floods in Recent Years .............................................................................................. 2-7 Table 2.7 Major Flood Disasters in Recent Years ................................................................................ 2-7 Table 3.1 Provisions for Simulation in Previous Study ....................................................................... 3-3 Table 3.2 Conditions for Flood Analysis ............................................................................................ 3-12 Table 3.3 Result of Annual Maximum Flood Discharge Estimation.................................................. 3-17 Table 3.4 Peak Time of Past Measure Floods .................................................................................... 3-19 Table 3.5 Selection of Past Floods ..................................................................................................... 3-21 Table 4.1 Conditions for Flow Capacity Calculation ........................................................................... 4-2 Table 4.2 Results of Flow Capacity Calculation .................................................................................. 4-2 Table 4.3 Design Freeboard ............................................................................................................... 4-10 Table 4.4 Proposed Projects by WB Study......................................................................................... 4-10 Table 4.5 Alternative Plans by WB Study .......................................................................................... 4-12 Table 4.6 Comparison of Previous Studies ........................................................................................ 4-14 Table 4.7 Summary of Rainfall Analysis ........................................................................................... 4-16 Table 4.8 Comparison of Rainfall Analysis in Previous Studies ........................................................ 4-16 Table 4.9 Results of Probable Rainfall Analysis ................................................................................ 4-17 Table 4.10 Cases of Design Hyetographs ........................................................................................... 4-17 Table 4.11 Design Hyetographs by Enlargement of Actual Past Hyetographs .................................. 4-17 Table 4.12 Water Level of Laguna Lake in Previous Studies ............................................................ 4-21 Table 4.13 Water Level of Laguna Lake in Previous Studies ............................................................ 4-22 Table 4.14 Water Level of Laguna Lake in Previous Studies ............................................................ 4-24 Table 4.15 Comparison of NHCS Operation ..................................................................................... 4-31 Table 4.16 Comparison of With/Without MCGS ............................................................................... 4-31 Table 4.17 Comparison of With/Without MCGS ............................................................................... 4-32 Table 4.18 Diversion Discharge With/Without MCGS ...................................................................... 4-32 Table 4.19 Reviewed Probable Discharge at Sto.Nino ...................................................................... 4-34 Table 4.20 Control Volume of Retarding Basin for 1/30 Flood ......................................................... 4-38 Table 4.21 Summary of Alternatives for 1/30 Years Flood Management .......................................... 4-40 Table 4.22 Comparison of Alternatives for 1/30 Years Flood Management ...................................... 4-41 Table 4.23 H-V Relation of Proposed Dam ....................................................................................... 4-49 Table 4.24 Specifications of Dams Examined ................................................................................... 4-50 Table 4.25 Specifications of Dams Examined ................................................................................... 4-51 Table 4.26 Specifications of Candidate Retarding Basin ................................................................... 4-52 Table 4.27 Flood Control Effect of Retarding Basin .......................................................................... 4-54 Table 4.28 Estimation Cases of Dam + Retarding Basin ................................................................... 4-54 Table 4.29 Flood Control Effect of Dam + Retarding Basin .............................................................. 4-54 Table 4.30 Alternatives for Urgent Flood Management Measures ..................................................... 4-58 Table 4.31 Alternatives for Urgent Flood Management Measures (Sto.Nino: 3,100 m3/s)................ 4-64 Table 4.32 Alternatives for Urgent Flood Management Measures (Sto.Nino: 2,900 m3/s)................ 4-65 Table 4.33 Comparison with Proposed Measures by WB Study ....................................................... 4-66 Table 4.34 Source of Cost Estimation ................................................................................................ 4-67 Table 4.35 Project Cost Allocation by Component ............................................................................ 4-68 Table 4.36 Cost Estimate of Retarding Basin .................................................................................... 4-70 Table 4.37 Cost Estimate of Dam ...................................................................................................... 4-71 Table 4.38 CPI of Metro Manila ........................................................................................................ 4-71 Table 4.39 Summary of Project Cost of Proposed Alternatives (2012 Price) .................................... 4-71 Table 4.40 Project Cost before Conversion ........................................................................................ 4-72 Table 4.41 Project Cost after Conversion (2012 Price) ...................................................................... 4-73


Final Report - 7 -

Table 4.42(1) Project Cost of WB Proposed Measures (2011 Price) ................................................. 4-74 Table 4.42(2) Project Cost of WB Proposed Measures (2012 Price) ................................................. 4-74 Table 4.43 Comparison of Project Cost between JICA Study and WB Study ................................... 4-75 Table 4.44 Conversion Factors ........................................................................................................... 4-75 Table 4.45 Economic Cost of the Target Case ................................................................................... 4-76 Table 4.46 Detail of Flood Damage ................................................................................................... 4-76 Table 4.47 Assets in the probable flood area ...................................................................................... 4-77 Table 4.48 Damage Rate of Residential Buildings in inundation depth............................................. 4-77 Table 4.49 Damage Rate of Household Assets in inundation depth .................................................. 4-78 Table 4.50 Damage Rate of Depreciable Assets and Stock Inventories in inundation depth............. 4-78 Table 4.51 Damage Rate of Agricultural Crops in inundation depth ................................................. 4-78 Table 4.52 Damage Amount by Probability year ............................................................................... 4-79 Table 4.53 Expected Amount of Average Annual Damage Reduction .............................................. 4-79 Table 4.54 Expected Amount of Average Annual Damage Reduction .............................................. 4-79 Table 4.55 Investigation Cases ........................................................................................................... 4-82 Table5.1 Availability of Hourly Rainfall and Water Level Data (EFCOS) .......................................... 5-1 Table 5.2 Availability of Daily Rainfall Data (PAGASA) ................................................................... 5-1 Table 5.3 Summary of Inflow Rivers to Laguna Lake ......................................................................... 5-9 Table 5.4 Instrumental Evaporation ( ) and Monthly Mean Value (mm/day) ................................... 5-9 Table 5.5 Data Availability of Adopted Rainfall Stations operated by PAGASA .............................. 5-10 Table 5.6 Rise Prediction of Global Average Ground Temperature and Sea Level Rise Prediction in

End of the 21st Century.............................................................................................................. 5-13 Table 5.7 Rainfall Increment Volume ................................................................................................. 5-15 Table 5.8 Amount of Monthly Evaporation change to 1 ℃of Temperature Rises (Manila) ............. 5-17 Table 6.1 Boundary Conditions by Climate Change ............................................................................ 6-1 Table 6.2 Probable Peak Discharges at Sto.Nino Station ..................................................................... 6-1 Table 6.3 Impact of Climate Change .................................................................................................... 6-2 Table 6.4 Available Structural Adaptation Measures for Alternatives A-1 to A-3 ............................... 6-8 Table 6.5 Available Structural Adaptation Measures for Alternatives O-1 to B-3 ............................... 6-8 Table 6.6 Proposed Non-Structural Adaptation Measures ................................................................... 6-9


Final Report - 8 -

ABBREVIATION

Abbreviat ion Engl ish

AOGCM Atmosphere-Ocean General Circulation Model

AR4 Fourth Assessment Report

ARMM Autonomous Region of Muslim Mindanao

AusAID Australian Agency for International Development

B/C Benefit/Cost Ratio

BOD Bureau of Design

BRS Bureau of Research and Standards

CAR Cordillera Administrative Region

CPI Consumer Price Index

CV CIRUCULO VERDE

D/D Detailed Design

DEM Digital Elevation Model

DFL Design Flood Level

DHWL Datum High Water Level

DPWH Department of Public Works and Highways

EFCOS Effective Flood Control and Operation System

EIRR Economic Internal Rate of Return

F/S Feasibility Study

GBHM Geomorphology-Based Hydrological Model

GCM General Circulation Model

GNI Gross National Income

H-Q Water Level-Discharge

H-V Water Level-Volume

HWL Hight Water Level

IDW Inverse Distance Weighted

IPCC Intergovernmental Panel on Climate Change

JBIC Japan Bank for International Cooperation

JICA Japan International Cooperation Agency

L/A Loan Agreement

LGU Local Government Unit

LiDAR Laser Imaging Detection and Ranging

LLDA Laguna Lake Development Authority

LWL Low Water Level


Final Report - 9 -

Abbreviat ion Engl ish

MCGS Marikina Control Gate Structure

MM Man-month(s)

MMDA Metro Manila Development Authority

MMHWL Mean Monthly Highest Water Level

MP Master Plan

MSL Mean Sea Level

MTPDP Medium Term Philippine Development Plan

MWSS Metropolitan Manila Waterworks and Sewerage System

NAIA Ninoy Aquino International Airport

NAMRIA National Mapping and Resourece Information Authority

NCR National Capital Region

NEDA National Economic and Development Authority

NHCS Napindan Hydraulic Contrpl Structure

NPC National Power Corporation

NPV Net Present Value

PAGASA Philippine Atmospheric, Geophysical and Astronomical Services Administration

PD Presidential Decree

PDFPFMM Phisical Development Framework Plan for Metropolitan Manila

PDP Philippine Development Plan

PMO-MFCP Project Management Office - Major Flood Control Projects

PMRCIP Pasig-Marikina River Channel Improvement Project

PPA Philippine Ports Authority

PRBFFWC Pampanga River Basin Flood Forecasting and Warning Center

RDC Regional Development Council

RIDF Rainfall Intensity-Duration Frequency

SAPROF Special Assistance for Project Formation

SCS Soil Conservation Service,United States

SiB2 Simple Biosphere Model 2

SPM Summary for Policymarkers

SRES Special Report on Emission Scenarios

SWL Surcharge Water Level

UPLB University of tha Philippines at Los Barios

WB The World Bank

WEB-DHM The Water And Energybudget-Based Distributed Hydrological Model

WL Water Level


Final Report - 10 -

UNIT (Length) mm : millimeter(s) cm : centimeter(s) m : meter(s) km : kilometer(s) (Area) mm2 : square millimeter(s) cm2 : square centimeter(s) m2 : square meter(s) km2 : square kilometer(s) ha : hectare(s) (Weight) g, gr : gram(s) kg : kilogram(s) ton : ton(s) (Time) s, sec : second(s) min : minute(s) h, hr : hour(s) d, dy : day(s) y, yr : year(s) (Volume) cm3 : cubic centimeter(s) m3 : cubic meter(s) l, ltr : liter(s) mcm : million cubic meter(s) (Speed/Velocity) cm/s : centimeter per second m/s : meter per second km/h : kilometer per hour

LIST OF SOURCE JICA 1990

The Study on flood control and drainage project in Metro Manila（1990） JICA 2011

THE PREPARATORY STUDY FOR PASIG-MARIKINA RIVER CHANNEL IMPROVEMENT PROJECT (PHASE III) IN THE REPUBLIC OF THE PHILIPPINES (OCTOBER 2011)

JICA 2013

Study of Water Security Master Plan for Metro Manila and its Adjoining Areas（2013）

WB 2012 Master Plan for Flood Management in Metro Mani la and Surrounding Areas Final Draft Master Plan Report

March 2012


Final Report 1-1

CHAPTER 1 INTRODUCTION

1.1 Background and Objective of Study

1.1.1 Background

The Pasig-Marikina-San Juan River System, of which total catchment area is 621 km2, runs through the center of Metro Manila and flows out to the Manila Bay. Its Main tributaries, the San Juan River and Napindan River, join the main stream at about 9.9 km and 19.9 km upstream from the Pasig River mouth, respectively. The three largest waterways contribute largely to the flooding in the metropolis brought about by the riverbank overflow of floodwaters. Metro Manila, which encompasses 16 cities and 1 municipality having a total projected population of over 11.5 million in 2010, is the economic, political and cultural center of the Philippines.

A Master Plan of flood control for the Pasig-Marikina River including the drainage in Metro Manila was prepared in 1954. In line with the flood control plan, the improvement works of the Pasig River, consisting mainly of river walls and revetments of the channel were constructed in the 1970’s. The Manggahan Floodway having a design flow capacity of 2,400 m3/s for diversion of flood from Marikina River to Laguna Lake was completed in 1988 to mitigate the flood damage due to the overflow of the lower Marikina River and Pasig River.

In addition to the Manggahan floodway, the necessity of river channel improvement of Pasig-Marikina River has been studied to cope with the existing flood problems in Metro Manila. The department of Public Works and Highways (DPWH) conducted an updated Master Plan (M/P) for flood control and drainage improvement in Metro Manila and a Feasibility Study (F/S) on the channel improvement of the Pasig-Marikina River from January 1988 to March 1990, under a technical assistance from the Japan International Cooperation Agency (JICA), called “The Study on Flood Control and Drainage Project in Metro Manila (JICA M/P Study).”

Based on the updating/review of the F/S for the river channel improvement project through the Special Assistance for Project Formulation (SAPROF) of Overseas Economic Cooperation Fund (OECF) in 1998, the “Pasig-Marikina River Channel Improvement Project (PMRCIP)” was proposed for the implementation in the following four phases under the financial assistance of Japanese ODA. The Preparatory Study for Pasig-Marikina River Channel Improvement Project (Phase II)” was also conducted in 2010-2011 under JICA technical cooperation, and the implementation of Phase II and III of PMRCIP is currently on-going funded by JICA.

On the other hand, the World Bank conducted the study “Master Plan for Flood Management in Metro Manila and Surrounding Areas” (“WB Study”) under the objective to establish the vision, which will be the blue print or road map, for a sustainable and effective flood risk management in Metro Manila and surrounding areas until 2035. The specific objectives are as follows;

- To carry out a flood risk assessment study from Metro Manila and surrounding areas - To prepare a comprehensive flood risk management plan; and - To propose a set of priority structural and non-structural measures that will provide sustainable

flood risk management up to a certain safety level

The WB Study has shown the results; 1) Review of current situation and arrangement of flood risk management, 2) Study on the mechanism of floods and flood damage, 3) Identification of constraints and barriers for flood risk management and directions for improvement, and 4) Formulation of the macro-framework for integrated flood risk management plan.

Based on the results of the WB Study and JICA M/P Study, JICA conducts “Data Collection Survey on Flood Management Plan in Metro Manila” to further examine with the detailed flood control measures in Pasig-Marikina River Basin.

JICA shall utilize effectively the related data and model established in the related studies such as:

- Cross-section data of the Pasig-Marikina River in the Detailed Design of the Pasig-Marikina River Channel Improvement Project (Phase III),

- Water and Energy Budge-based Distribution Hydrological Model (WEB-DHM) and results of


Final Report 1-2

rainfall analysis obtained in “the Study of Water Security Master Plan for Metro Manila and its Adjoining Areas” (hereinafter referred to as the “JICA Water Security Study”)

1.1.2 Objective The objective is to reexamine the technical validity of the proposed structural measures in Pasig-Marikina River Basin under the WB Study by utilizing the hydrological and hydrodynamic flood simulation model which is to be refined and updated with appropriately selected dataset in consideration of the future climate change; thereby bridging the concept planning and the actual implementation of projects.

1.2 Study Framework

1.2.1 Study Area Study area is to Pasig-Marikina River Basin and Laguna Lake Basin in Metro Manila.

1.2.2 Summary of Study Purposes, Outputs and Activities

Project activities and purposes are summarized as follows.

<Overall Goal>

Basic data and information for practical flood management plan is prepared by reviewing previous study results such as design flood discharge prepared by WB considering future climate change.

<Project Purpose> Technical validity of the proposed structural measures under WB Study is reexamined by utilizing the hydrological and hydrodynamic flood simulation model which is to be refined and updated with appropriately selected dataset in consideration of the future climate change.

<Outputs>

1. Climate change effect is analyzed. 2. Different rainfall patterns from Ondoy Typhoon are analyzed. 3. Discharge distribution plan is reviewed. 4. Future practical countermeasures are planned considering current level of river improvement in

Pasig River.

Activities

1) Collection and Utilization of Previous Study Results

Runoff Characteristics of Pasig-Marikina River and Laguna Lake Basins Hydrological Data, Data related River Course and Inundation

2) Establishment of Flood Analysis Model

Integration of Runoff Analysis Model, River Course Hydraulic Model and Inundation Model

3) Analysis of Design High-water Discharge

Examination of Previous Rainfall Analysis Setting of Basic Flood Discharge Examination of Planning Conditions and Parameters in Previous Studies


Final Report 1-3

Setting of Design Flood Discharge Examination of Validities of Flood Control Facilities (Cost & Benefit Analysis)

4) Analysis of Water Level Fluctuation in Laguna Lake during Flood in Pasig-Marikina River

Validity of Flood Management Measures considering Effect to Laguna Lake

5) Analysis of Climate Change Effects

Runoff Analysis considering Climate Change Effect Examination of Climate Change Effect such as Change of Safety Degree Proposal of Adaptation Measures against Climate Change

6) Information Sharing with Other Developing Partners

7) Assistance of Steering Committee

1.2.3 Counterpart Agency by Philippines Side

The counterpart agency is Department of Public Works and Highway (DPWH) of the Republic of Philippine.

1.3 Schedule of Study The Study has been conducted from April 2013 to May 2014 as shown in Table 1.1.

Table 1.1 Schedule of Study

3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6

IC/R TN1 TN2 DF/R F/RReport

Item 2013 2014

Work in Japan

Work in Philippines

IC/R: Inception Report, TN1: Technical Note-1, TN2: Technical Note-2, DF/R: Draft Final Report, F/R: Final Report

Summary of the works of each work period are as follows.

[Preparatory Works in Japan (Beginning of April, 2013)]

Analysis of Existing Reports and Documents, Study Planning, Preparation of Inception Report

[1st Work in Philippine (April 3 to 13, 2013)]

Inception Report Meeting, Meeting with the WB

Site Reconnaissance: Pasig-Marikina River, Manggahan Floodway, Napindan Channel, Laguna Lake, San Juan River

Data and Information Collection

[1st Work in Japan (Middle of April to End of May, 2013)]

Analysis of Collected Data and Information

Establishment of Flood Analysis Model: Preparation of River Cross Section Data and DEM Analysis and Calculation of H-Q Equation


Final Report 1-4

Estimation of Peak Discharge of Typhoon Ondoy Selection of Past Floods Calibration of Parameters and Verification of Model

Establishment of Water Level Fluctuation Model in Laguna Lake: Verification of Data Availability Analysis of Water Level Fluctuation Properties Examination of Concepts of Model Establishment and Conditions

Preparation of Technical Note-1

[2nd Work in Philippine (June 3 to 11, 2013)] Meeting on Technical Note-1:

PMO, FCSEC, BOD, BRS, MMDA

Site Reconnaissance: Upper-upper Marikina River, Expected Dam Sites, Manggahan Floodway


[2nd Work in Japan (Middle of June to End of July, 2013)]

Analysis of Collected Data and Information

Review of Rainfall Analysis and Setting of Design Rainfall

Estimation of Basic Design Discharge

Estimation of Design Flood Discharge and Proposal of Flood Management Measures: Review of Preconditions (Current Flow Capacity, Plan of PMRCIP, Proposed Plan by the

WB, Existing Structures) Estimation of Design Flood Discharge (Evaluation of Design Flood Discharge of PMRCIP,

Operation of NHCS, Necessity of MCGS) Examination of Flood Management Measures against 1/30 and 1/100 Years Probable Floods Preliminary Examination of Dam and Retarding Basin Preparation of Technical Note-2

Establishment of Water Level Fluctuation Model in Laguna Lake:

Establishment of Model and Analysis of Water Level Fluctuation Flow Analysis in Napindan Channel during Flood Analysis of Impact of Flood Management Measures to Water Level of Laguna Lake Analysis of Impact of Climate Change to Water Level of Laguna Lake

Preparation of Technical Note-2

[3rd Work in Philippine (July 31 to August 11, 2013)] Meeting on Technical Note-2:

PMO, BOD, BRS, MMDA

Meeting with the Secretary of DPWH


[3rd Work in Japan (Middle of August to Beginning of September, 2013)] Analysis of Collected Data and Information

Establishment of Phased Development Scenarios

Cost Estimate and Economic Evaluation

Analysis of Water Level Fluctuation in Laguna Lake: Examination Validity of Flood Management Measures

Analysis of Impact of Climate Change to Flood Management of Pasig-Marikina River


Final Report 1-5

Preparation of Draft Final Report

[4th Work in Philippine (September 5 to 12, 2013)] Meeting on Draft Final Report

Technical Working Group Meeting


Meeting with WB

[4th Work in Japan (Middle of September, 2013 to Beginning of February, 2014)] Preparation of Additional Explanation for Comments on Draft Final Report

Preparation of Meeting Materials

[5th Work in Philippine (February 10 to 14, 2014)]

Meeting on Results of Study and Direction of Improvement

Technical Working Group Meeting


Meeting with WB

[5th Work in Japan (Middle of February to End of May, 2014)]

Preparation of Final Report


Final Report 1-6

CHAPTER 1 INTRODUCTION ................................................................................................... 1-1 1.1 Background and Objective of Study .................................................................................. 1-1

1.1.1 Background ............................................................................................................. 1-1 1.1.2 Objective.................................................................................................................. 1-2

1.2 Study Framework ............................................................................................................... 1-2 1.2.1 Study Area .............................................................................................................. 1-2 1.2.2 Summary of Study Purposes, Outputs and Activities ......................................... 1-2 1.2.3 Counterpart Agency by Philippines Side .............................................................. 1-3

1.3 Schedule of Study ............................................................................................................... 1-3


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CHAPTER 2 CONDITIONS OF BASIN

2.1 Natural Conditions of Basin

2.1.1 Topography and Geology

Luzon Island is topographically divided into three areas, namely North Luzon, Central Luzon and South East Luzon. Central Luzon including the Study area is structural geologically divided into Zambales Range in west, Central Valley in center and southern slope of Sierra Madre Mountains. Sierra Madre Mountains where upstream area of the basin is included consists of Cretaceous to Tertiary Periods soils such as limestone, tuff and several magmatic rocks.

Between Sierra Madre Mountains and Manila Delta is Marikina Valley consisting alluvial deposits such as sand gravel silt and clay. Depth of alluvial deposit varies randomly such as 120m at North Montalban, 15m at Marikina, and 40m at Pasig. Manila Delta is flat and consists of alluvial soil. Depth of alluvial deposits is more than 70m near the coast but relatively thin at Santa Messa, Makati and east Marikina areas.

2.1.2 Climate

Climate of Philippines are governed by monsoon, trade wind, tropical depression and their combinations. Typhoon has the most effect on flood. 20 to 30 typhoons pass on or near Philippines annually, and 20% of them pass on Central Luzon. Figure 2.1 shows average monthly rainfall and temperatures. Season is divided into two, rainy season from May to October and dry season from November to April.

Source: JICA Study Team

Figure 2.1 Average Monthly Rainfall, Average Minimum and Maximum Temperatures in Metro Manila

Rainfall is concentrated in rainy season from May to October when about 90% of annual rainfall


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comes down mainly induced by monsoon and typhoon.

Maximum temperature rises up to 33oC in April-May when transition period from dry season to rainy season, and declines to less than 30oC in December-January, however, seasonal variation is very small.

2.1.3 Land Use Conditions

Land use conditions is summarized based on the land use map by NAMRIA in 2005 as shown in Figure 2.3. Forest and woodland occupies about 61% which dominant in upstream basin while built-up area is 27% mainly in Metro Manila.


Figure 2.2 Land Use of Pasig-Marikina River Basin (as of 2005)


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2.1.4 Social Economy Conditions

(1) Outline of Relevant Governance Zones Pasig-Marikina River is an urban river with a catchment area of 635 km2, which runs from Rodriguez City in Rizal Province through the administrative and economical epicenter in National Capital Region (NCR) and finally flows into Manila Bay. The Pasig-Marikina River connects with Laguna Lake by way of the Napindan Channel and Mangahan Floodway.

The study area is the water area of 11 cities and municipalities in NCR and Rizal Province shown in Table 2.2. These cities and municipalities have made a rapid economic and population growth.

Table 2.1 Area of Relevant Governance Zones Division Governance Zone Jurisdictional Area (km2)

NCR

Makani City 21.57 Mandaluyong City 9.29 Manila City 24.98 Marikina City 21.52 Pasig City 48.46 Quezon City 171.71 San Juan City 5.95 Pateros Municipality 10.40 Taguig City 45.21

Rizal Province Cainta Municipality 42.99 Taytay Municipality 38.80 Total 440.88

Source：2010 Census of Population and Housing Report No.3 Population, Land Area, and Density

(2) Population and Population Density in Relevant Governance Zones

There is difference in zones like that the population in Manila City and San Fuan City have increased or decreased slightly, but that in the remaining cities/municipalities has increased steeply.

The study area has made a rapid population growth and this tendency seems to be continued in future. In 2010, Taguig City, Cainta City and Taytay City increased their population more than 100 percent compared with 1990.

From population density, that in Manila City is more than 66,000 people/km2 and that in the others come within the range between 6,000 people/km2 and 35,000 people/km2, even though these figures are equal to or higher than that in Tokyo with 6,000 people/km2 as of October 2013 in first place of Japan.

Table 2.2 Population of Relevant Governance Zones

Division Governance Zone Population (people) and Population Density

(people/km2)* 1990 2000 2010

NCR

Makani City 453,170 (21,009)

471,379 (21,853)

529,039 (24,527)

Mandaluyong City 248,143 (26,711)

278,474 (29,976)

328,699 (35,382)

Manila City 1,601,234 (64,101)

1,581,082 (63,294)

1,652,171 (66,140)

Marikina City 310,227 (14,416)

391,170 (18,177)

424,150 (19,710)

Pasig City 397,679 (8,206)

505,058 (10,422)

669,773 (13,821)

Quezon City 1,669,776 (9,724)

2,173,831 (14,463)

2,761,720 (16,903)


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San Juan City 126,854 (21,320)

117,680 (19,778)

121,430 (20,408)

Pateros Municipality 51,409 (4,943)

57,407 (5,520)

64,147 (6,168)

Taguig City 266,637 (5,898)

467,375 (10,338)

644,473 (14,255)

Rizal Province Cainta Municipality 126,839

(2,950) 242,511

(5,641) 311,845

(7,254)

Taytay Municipality 112,403 (2,897)

198,183 (5,108)

288,956 (7,447)

Total 5,364,371 6,484,150 7,796,404 Note; The upper row : population, the lower row : population density

Source：2010 Census of Population and Housing Report No.3 Population, Land Area, and Density (3) Economic-related Matters

The Philippine’s economic growth rate was sluggish temporarily but it achieved 7 percent in 2012. And GNI per capita in 2012 reached US$ 4,380, this increased 20 % of that in 2008 as US$ 3,640. (refer to Table 2.4) However, Haiyan Typhoon killed thousands of people and destroyed a lot of residential houses and infrastructures of some islands in Central Visayas and Palawan Province on Nov. 8, 2013. Thus, the Philippines has frequently been damaged by natural disasters such as Typhoons.

NCR takes on the responsibility of acting the capital of Philippine centering on Manila City, and the Pasig-Marikina River runs through this zone as previously mentioned.

NCR came into being with 8 cities and 9 municipalities that were integrated from 4 cities (Manila City and Quezon City etc.) and 13 municipalities (Makati Municipality, Marikina Municipality and Muntinlupa Municipalty etc.) following Presidential Decree No. 824 in 1975.

As shown in Table 2.5, most of this zone was covered by agricultural and forest land in 1938, and residential, commercial and industrial area account for more than 70 percent of it in 1990 as a result of rapid urbanization in and after 1980.

Table 2.3 Basic Economic Indicator of Philippines

Item 2008 2009 2010 2011 2012 GNI per capita, PPP (US$) 3,640 3,650 3,920 4,070 4,380 Population (thousand person) 90,371 91,886 93,444 95,053 96,707 GDP (million US$) 173,603 168,334 199,589 224,095 250,182 GDP growth (annual %) 4 1 8 4 7

Source：The World Bank World Data Bank

Table 2.4 Changes in Urbanization of NCR (1938 – 1994)

Item Proportion (%) 1938 1980 1990 1994

Residential 14.2 29.4 65.0 65.0 Commercial - 3.0 3.4 8.0 Industrial - 4.7 4.0 3.0 Institutional - 4.5 5.2 10.6 Utilities - 1.4 4.0 4.0 Agricultural 55.6 12.5 8.4 4.4 Open Space 5.1 24.3 8.0 4.0 Forest Land/Parks 25.1 20.2 2.0 1.0

Total 100.0 100.0 100.0 100.0 Source：Philippine Institute for Development Studies, DISCUSSION PAPER SERIES NO. 2000-20


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1) Development Plan

A Medium-Term Philippine Development Plan (MTPDP) remains in force for six years, corresponding to the term of office of the country’s president (however, the recent plan is a five-year plan, “Philippine Development Plan 2011 – 2016” (PDP), starting from the second year of the presidency). MTPDP is summarized as follows; MTPDP includes major policy initiatives, socioeconomic strategies, and major national

programs. Meanwhile, regional development plans stipulate strategies, programs and projects that facilitate

the goals of the national plans. The National Economic and Development Authority (NEDA), which charged with drafting the

MTPDPs, coordinates with related agencies in formulating the plan. The final product is subject to the approval by a NEDA committee made up of government cabinet members (the “Cabinet Committee”) and chaired by the president.

Regional Development Council (RDC) organized in each region (except for NCR, Autonomous Region in Muslim Mindanao (ARMM) ) is the counterparts of NEDA regional office established in each region that decides how plans should be implemented at the regional and municipal levels.

Each RDC is made up of regional/municipal representatives, representatives from government departments in the region, and members of the private sector.

NCR is the only urban area in the country of which its geographical area and administrative power is legally defined (by 1995 Act for creating Metro Manila Development Authority). After Metropolitan Manila Authority (MMDA), the government agency, came into being in 1995, the first special planning document it issued was the “Physical Development Framework Plan for Metropolitan Manila, 1996 – 2016” (PDFPFMM). The plan was amended in 1999 and is maintained until now, but at the moment in February 2012, to replace it, formulation of a plan called “Metro Manila Green Print 2030” is under preparation. As a plan corresponding to Regional Development Plans of other regions, Regional Development Plan for the National Capital Region 2010 – 2016 (RDP – NCR) was established.

Source：Metro Manila Development Authority (1999) “A Physical

Development Framework Plan for Metropolitan Manila, 1996 – 2016”

2) Industrial Cluster Strategy The Philippine Development Plan 2011 – 2016 (PDP) sets out “Industrial Cluster Strategy” to promote creation of industrial clusters (geographical accumulation of specific industry) reflecting industrial activity and infrastructural character of respective domestic area which will contribute to the creation of regional wealth through export. In this strategy, through developing industrial clusters, the government intends to promote fostering of inter-business cooperation between small and medium tiny companies to strengthen network toward collaboration, and this is based on the understanding that the past development policy had lead the country to “fall into the path of a trickle-down theory jobless growth” (Trickle-down theory is an economic thought that expresses vitalization of economic activities of large enterprises and wealthy class will make a stream of wealth pouring down onto low-income class that will finally bring benefit to the whole nation.) The priority industrial cluster for NCR are Health and Wellness as shown in Table below.


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Table 2.5 Priority Industrial Clusters (2011 – 2016)

Region Area Industrial Cluster

North Luzon

CAR (Cordillera Administrative Region)

Coffee

R1 (Ilocos) Milkfish R2 (Cagayan Valley) Dairy and Dairy Products R3 (Central Luzon) Bamboo and Logistics

South Luzon

R4A (Calabarzon) ICT and IT-enabled Services and Logistics R4B (Mimaropa) Eco-Tourism R5 (Bicol) Wearable and Lifestyle NCR (National Capital Region) Health and Wellness

Visayas

R6 (Western Visayas) Gifts, Toys and Housewares, Health and Wellness, Food, ICT, Eco-Tourism

R7 (Central Visayas) Gifts, Toys and Housewares, Health and Wellness, Food, ICT, Eco-Tourism

R8 (Eastern Visayas) Gifts, Toys and Housewares, Food, Eco-Tourism Mindanao All Banana, Mango, Seaweed, Wood, Coconut, Mining,

Eco-Tourism, ICT Source：National Economic Development Agency (2011) “Philippine Development Plan 2011 – 2016”

2.2 River Conditions

Pasig-Marikina River runs through Metro Manila into Manila Bay. Catchment area is about 635km2 and 20% of it is within Metro Manila.

2.2.1 Pasig River Pasig River has a length of 17.1km from river mouth to Napindan Hydraulic Control Structure (NHCS), with average riverbed slope of 1/10,000, river widths of 60m – 250m and depths of 6m – 12m. San Juan River is the major tributary which flows into Pasig River at 7.1km from the river mouth. Most of cross section is single section with revetment and parapet. From the river mouth to Delpan Bridge located at 700m from the river mouth, both river banks are utilized as wharf of Manila Bay operated by Philippine Port Authority (PPA).

Pasig River has an important role of regional economy as river transportation in whole section, especially in the section from Delpan Bridge to Jones Bridge there are many berths for factories at both sides. DPWH has conducted dredging work from the river mouth to Jones Bridge for river transportation.

2.2.2 Marikina River Marikina River can be divided into three sections, namely lower Marikina from NHCS to the diversion to Manggahan Floodway with length of 7.2km, upper Marikina from Manggahan to Sto. Nino with length of 6.1km, and upper-upper Marikina from Sto. Nino to Montalban Bridge with length of 14.4km.

In the lower Marikina River, riverbed slope is less than 1/5,000, river widths are 90m – 100m, and depths are 4.2m – 9.5m. Cross section is single section with natural dyke, and foot paths are installed at middle section of the lower Marikina River. Bank protection works is merely conducted and the river area is covered by bush. There are many small houses and factories along the river.

In the upper Marikina River, riverbed slope is about 1/5,000 and river widths are 70m – 200m. Cross section is single section with natural dyke, and foot paths and parks are developed. As well as the lower Marikina River, bank protection works is merely conducted and the river area is covered by bush. There are many small houses along the river, but factory is few.


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In the upper-upper Marikina River, riverbed slope becomes steeper about 1/1,450 and river widths are 70m – 350m. Cross section is composite section consisting of low flow channel and natural retarding basin. In the most section between Sto. Nino to the confluence of Nangka River, there are houses along river course while it is sparse between the upstream of confluence of Nangka River to Montalban Bridge.

2.3 Major Flood Disasters Metro Manila suffers from flood disasters mainly during May to November due to typhoon and southwest monsoon. Major floods and their disasters in recent years are summarized in Table 2.1 and 2.2.

Table 2.6 Major Floods in Recent Years

Year Month Storm Sto.Nino Peek WL (m)

Average-Rainfall over watershed (mm/1day)

2000 11 Seniang 18.01 149.0

2003 5 Chedeng 17.76 189.4

2004 11 Winnie 19.08 190.2

2009 9 Ondoy 22.16 290.8

2012 8 Kirogi 20.42 271.7 Source: JICA Study Team

Table 2.7 Major Flood Disasters in Recent Years

Year Month Storm No. of Affected Casualties Total

Damage (mil. Peso) Family Persons Dead Injured Missing

2000 11 Seniang 14,818 77,899 3 N.A. N.A. N.A.

2003 5 Chedeng 2,227 11,144 0 0 0 N.A.

2004 11 Winnie 5,873 27,284 1 0 0 N.A.

2009 9 Ondoy 174,408 872,097 241 394 0 290

2012 8 Kirogi 90,121 419,555 41 4 2 410 N.A. : not available, Source: JICA Study Team


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CHAPTER 3 ESTABLISHMENT OF FLOOD ANALYSIS MODEL

3.1 Establishment of Flood Analysis Model Flood analysis model was established integrating runoff analysis model (WEB-DHM Model), river hydraulic model (one dimensional unsteady flow model) and inundation analysis model (two dimensional unsteady flow model).

3.1.1 Runoff Analysis Model (WEB-DHM) Runoff model was established based on data related to runoff characteristics such of area of basin, elevation, slope, landuse, vegetation, soil and so on. For establishing model, “Water and Energy Budget-based Distributed Hydrological Model” (WEB-DHM) which was established in in the Study of Water Security Master Plan for Metro Manila and its Adjoining Areas (hereinafter referred to as “JICA Water Security Study”) was utilized.

Distributed type runoff analysis model can describe spatial variations of basin such as topography, dynamic behavior of rainwater, soil characteristics, spatial variation of rainfall and so on. WEB-DHM has been developed by fully coupling of a biosphere scheme (SiB2) with a distributed type runoff model named geomorphology-based hydrological model (GBHM). The SiB2 described the transfer of turbulent fluxes such as energy, water and carbon fluxes between the atmosphere and land surface for each model grid. The GBHM redistributes water moisture laterally trough simulation of both surface and subsurface runoff using grid-hill slope discretization and then flow routing in the river network.

Outline of the model, area and basin segmentation for the modeling are shown in Figure 3.1 to 3.3.

Source: WEB-DHM and IWRM, The 4th GEOSS AWCI ICG Meeting, Kyoto, 6-7 February 2009

Figure 3.1 Outline of WEB-DHM Model

Necessary Data Soil Class Vegetation Leaf Area Index and Photosynthetically Active Radiation Absorption Factor Relative Humidity Insolation Time Temperature Wind Velocity Air Pressure Hourly Rainfall in Basin Division


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Source: Study of Water Security Master Plan for Metro Manila and its Adjoining Areas

Figure 3.2 Area for Modeling

a. Digital Elevation Model b. Slope Angle c. Sub-Basins


Figure 3.3 Basin Segmentation for Modeling


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3.1.2 Inundation Model

(1) Model in Previous Study The following items were examined for the river hydraulic model and inundation analysis model which established in the Preparatory Survey on Pasig-Marikina River Channel Improvement Project (Phase III).

River Hydraulic Model (One-dimensional Non-uniform Flow Model): River Course Characteristic Data (River Networks, Cross Sections and Their Intervals, Hydraulic Constants, Downstream Boundary Conditions, Water Levels in Manila Bay and Laguna Lake)

Inundation Analysis Model (Two-dimensional Unsteady Flow Analysis Model): Simulated Inundation Area, Landuse, Vegetation, Soil and so on.

Table 3.1 Provisions for Simulation in Previous Study

Item Description Method River Course: One-dimensional Unsteady Flow Model

River Basin: Two-dimensional Unsteady Flow Analysis Model River Conditions Current and After Improvement (Phase III) Roughness Coefficient in Land 0.050 (Standard Value) Mesh Size 100m×100m Overflow Discharge when Dike Break Overflow discharge is estimated by Honma’ Formula Boundary Conditions Manila Bay: Mod; Curve (Max. MMHWL 11.4 E.L.m)

Laguna Lake: 12.2E.L.m (Average W.L duirng Flood) (Refer to D/D Report in 2002)

Inflow Discharge Estimated Hydrograph of Typhoon Ondoy Source: Preparatory Survey on Pasig-Marikina River Channel Improvement Project (Phase III) (JICA)

(2) Inundation Model Flood analysis model is to combine above mentioned runoff model with river hydraulic model utilizing one-dimensional unsteady flow analysis model and inundation model utilizing two-dimensional unsteady flow analysis model.

Features of inundation model utilizing two-dimensional unsteady flow analysis model and image of model are shown in Figure 3.4. ＜Features of Model＞

Compound Inundation Phenomena of Inland Water Inundation and Flood can be reproduced. In flood plains, runoff phenomena and inundation phenomena can be analyzed as phenomena

happened simultaneously at same place. Chronological change of river water level can be reproduced considering change of water level

at downstream boundary and runoff discharge from upstream, and effects of river crossing facilities such as bridge.

Flow resistance due to landuse and density of building can be considered in the simulation of expanding of inundation areas and its velocities.

Effects of channels, embankment and micro-topography can be reproduced in high accuracy. Effects of drainage by sluice way or pump with various conditions of inland and river water

levels can be reproduced. Flood control function by storage facilities can be reproduced.


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Figure 3.4 Outline of River Hydraulic Model and Inundation Analysis Model

1) Target Area for Inundation Analysis The target area for inundation analysis was set as shown in Figure 3.5. The boundary was determined by examining several cross sections as shown in Figure 3.6 to 3.9.


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Figure 3.5 Target Area for Inundation Analysis


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Figure 3.6 Cross Sections for Setup of Target Area (1/4)


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2) Preparation of Mesh Elevation Data

Based on the survey conducted from December, 2010 to January 2011, LiDAR data was created with 1m x 1m mesh. Based on this data, 100m x 100m mesh elevation data was created. DEM data frameworks and created 100m x 100m mesh elevation data are shown in Figure 3.10 and 3.11, respectively.

It is noted that the LiDAR data was formulated by Enhancing Risk Analysis Capacities for Flood, Tropical Cyclone Severe Wind and Earthquake for Greater Metro Manila Area Component 5 of the Metro Manila Post‐Ketsana Recovery and Reconstruction Program by AusAID.


Figure 3.10 DEM Data Frameworks


Final Report 3-11


Figure 3.11 100m x 100m Mesh Elevation


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3) Conditions for Flood Analysis

The following conditions shown in Table 3.2 were applied for flood analysis. Floodplain model is shown in Figure 3.12.

Table 3.2 Conditions for Flood Analysis

Item Conditions

Method River Course: One-dimensional Unsteady Flow Model River Basin: Two-dimensional Unsteady Flow Analysis Model

River Course

Conditions

Area

Pasig-Marikina (-2.800k - 44.770k) San Juan (0.000k - 10.500k) Napindan Channel (0.000k - 8.176k) Manggahan Floodway (0.000k - 8.200k)

Interval About 100m - 200m Cross Section Section in Year 2010

Boundary Conditions Manila Bay: Observed Hydrograph Laguna Lake: Observed Hydrograph

Roughness Coefficient

Pasig-Marikina (-2.800k - 30.350k) : 0.028 Marikina (30.350k - 44.770k) : 0.030 San Juan (0.000k - 10.500k) : 0.030 Napindan Channel (0.000k - 8.176k) : 0.030 Manggahan Floodway (0.000k - 1.150k) : 0.021 Manggahan Floodway (1.200k - 8.200k) : Low Flow Channel 0.030 : Flood Channel 0.300

Floodplain Conditions

Inundation Type Upstream of SanMateo: Flow along River Type Downstream of SanMateo: Dispersion Type

Elevation 100m x 100m Mesh Elevation (based on LiDar Data) Roughness Coefficient 0.05 Overflow Condition Comparison of Dyke Elevation and Land Elevation


Final Report 3-13


Figure 3.12 Floodplain Model


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3.2 Calibration of Model with Past Floods

Validity of established flood analysis model was calibrated comparing the observed discharge and water level data with simulation results such as discharge, river water level and inundation level.

3.2.1 Verification of H-Q Equations

(1) H-Q Equations in Previous Studies H-Q equations were established in Preparatory Survey on Pasig-Marikina River Channel Improvement Project (Phase III) (hereinafter referred to as the “JICA Study”) and Master Plan for Flood Management in Metro Manila and Surrounding Areas (hereinafter referred to as the “WB Study”), respectively. These H-Q equations are quite different. By the H-Q equation in the JICA Study, the peak discharge of 2009 Flood is calculated at 3,211 m3/sec. On the other hand, it becomes 3,950 m3/sec by the H-Q equation in the WB Study, resulting more than 700 m3/sec deviation. Each H-Q equation was formulated as follows.

1) JICA Study

In the JICA Study, same H-Q equation was utilized which was formulated by “The Study on Flood Control and Drainage Project in Metro Manila” (hereinafter referred to as the “JICA M/P Study”) in 1990. This H-Q equation was calculated based on observed water level and discharge data from 1958 to 1987 as shown in Figure 3.13.

Source: The Study on Flood Control and Drainage Project in Metro Manila, JICA

Figure 3.13 H-Q Curve Formulated in JICA M/P Study


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2) WB Study

Although it seemed that the utilized data was limited, the WB Study also utilized same observed data during 1958 – 1987 as the JICA M/P Study. Besides, estimated discharge using uniform flow equation based on observed water level data after 1994 were also utilized as shown in Figure 3.14. It is noted that roughness coefficient of n=0.033 and slope of 1/1,500 was applied for estimation of discharge.

Source: Master Plan for Flood Management in Metro Manila and Surrounding Areas, the World Bank

Figure 3.14 H-Q Curve Formulated in WB Study

(2) Recalculation of H-Q Equation

H-Q equation was recalculated in the Study in order to verify the previous H-Q equations. Since observation of discharge has not conducted since 1994, discharge was estimated using non-uniform flow calculation.

1) Conditions for Non-uniform Calculation

The following conditions were applied for non-uniform calculation.

Utilized Water Level: Annual Maximum Water Level since 1994

Section for Calculation: Rosario Weir to Sto.Nino Station

Cross Section: Composite Data of Topographic Survey in 2010 and LiDAR Data

Downstream Boundary: Water Level at Rosario Junction Side Station when Maximum Water Level at Sto.Nino Station

Roughness Coefficients: the following coefficients were applied for riverbed, riverbank and flood channel referring to the “Hydraulic Formulas” in Japan.

Riverbed: 0.022 as standard value of natural straight uniform section channel Riverbank: 0.030 considering vegetation on riverbank Flood Channel: 0.050 as standard value of flood channel with trees

Composite roughness coefficient of river course and flood flow section including flood channel were about 0.024 and 0.028, respectively. It is noted that the composite roughness coefficient is same as the JICA Study. The cross section and site photos of Sto.Nino Station are shown in Figure 3.15 to Figure 3.17.


Final Report 3-16


Figure 3.15 Cross Section of Sto.Nino Station

Source: The preparatory study for sector loan on disaster risk managemnet in the Republic of Philippines, JICA 2010

Figure 3.16 Sto.Nino Bridge


Figure 3.17 Upstream of Sto.Nino Bridge


Final Report 3-17

Annual maximum flood discharges were estimated by trial calculation changing inflow discharges as shown in Table 2.3. As a result of calculation, energy gradients around Sto.Nino Station during 1994 flood were 1/2,500 to 1/3,000.

Table 3.3 Result of Annual Maximum Flood Discharge Estimation

Year Water Level (m)

Estimate Discharge (m3/s) Year Water Level

(m) Estimate Discharge

(m3/s)

1994 16.33 890 2004 19.08 1,940 1995 18.4 1,600 2005 16.03 760 1996 16.08 770 2006 16.37 890 1997 17.16 1,120 2007 16.9 1,040 1998 18.41 1,580 2008 16.74 1,020 1999 18.3 1,570 2009 22.16 3,480 2000 19.02 1,880 2010 NA NA 2001 16.31 860 2011 19.13 1,920 2002 17.94 1,410 2012 20.42 2,570 2003 17.76 1,330


2) Range of H-Q Recalculation

The number of observed water level and discharge data utilized for H-Q calculation in the JICA M/P is large in low flow discharge while the number of observed data more than 14m of water level is only 13 data. Thus, H-Q equation more than 14m was recalculated since H-Q equation by the JICA M/P Study less than 14m was expected to be high accuracy due to the number of observed data.

3) Result of Recalculation of H-Q Equation H-Q equation more than 14m of water level was recalculated based on the observed data during 1958 – 1987 and the estimated data after 1994 as shown in Figure 3.18. The peak discharge of 2009 Flood of which water level is 22.16m is calculated at 3,500 m3/sec.


Figure 3.18 Recalculated H-Q Curve


Final Report 3-18

(3) Validity of Previous H-Q Equations

The H-Q equations in previous studies are evaluated as follows.

<JICA Study> H-Q equation was estimated based on observed data. However, number of data during flood is very few. Only 1 data was available for more than 2,000m3/sec and reliability of this data was low comparing other observed data. Thus, it is judged that H-Q equation in low water has high accuracy but in high water more than 2,000m3/sec discharge is not.

<WB Study>

H-Q equation was estimated using estimated discharge data as well as observed data including high water more than 2,000m3/sec discharge. However, the followings can be pointed out regarding the accuracy of H-Q equation.

In the WB Study, energy gradient of 1/1,500 was applied for uniform calculation. However, it is considered as too high because the energy gradients of annual maximum discharge were estimated as 1/2,500 to 1/3,000 by the non-uniform calculation conducted by the Study.

In the WB Study, roughness coefficient of n=0.033 was applied for whole section, while 0.022 and 0.030 were applied for low flow channel and riverbank in the Study. As shown in Figure 2.13, the H-Q curve by the Study is quite similar to the H-Q curve by the JICA Study especially at the range of 14m to 16m water level. Since the H-Q curve by the JICA Study was based on observed data, it is expected that actual roughness coefficient of low flow channel is about 0.023, and the value applied in the WB Study, n=0.033, is considered as relatively high.

Larger energy gradient causes more discharge while larger roughness coefficient causes smaller discharge. In this case, much difference of energy gradient effects to larger discharge.

As a conclusion, H-Q curve by the JICA of which water level up to 14m and the new H-Q curve for more than 14m water level which is recalculated by the Study are applied for further analysis in the Study.

3.2.2 Peak Water Level by Typhoon Ondoy at Sto.Nino Station

During the flood by Typhoon Ondoy, water level was not recorded at Sto.Nino Station after 18:00 on September 26 with the record of 22.16m, and the peak water level is uncertain. Thus, the peak time of Sto.Nino during the flood by Typhoon Ondoy is estimated comparing the hydrographs of past measure floods at Montalban and Rosario JS Stations. Hydrographs of floods in 2000, 2004, 2009 (Typhoon Ondoy), 2011 and 2012 and their peak time are summarized in Table 3.4 and Figure 3.19 to Figure 3.23.

Difference of peak times between Montalban and Sto.Nino varies from 1 to 3 hours. And the peak water level by Typhoon Ondoy might not be recorded at Montalba also. On the other hand, hydrographs at Rosario JS has same tendency with St. Nino, and difference of peak time is 1 or 2 hours. Out of examined 5 major floods, the floods in 2011 and 2012 were induced by monsoon and several peaks were observed. The floods in 2000 and 2004 were induced by Typhoon, which must have a same tendency in the hydrograph with Typhoon Ondoy. Difference of peak time between Rosario JS and Sto.Nino during 2000 and 2004 floods are 1 hour.

Based on the non-uniform flow calculation, average flow velocity between Sto.Nino and Rosario JS is estimated at 2.5m/sec. Applying this value, flood arrival time from Sto.Nino to Rosario JS is estimated as 6,550m / 2.5m/sec = 2,620 sec = about 44 minutes.

Based on above examinations, difference of peak time between Sto.Nino and Rosario JS is estimated at 1 hour and the peak time of Sto.Nino during the flood by Typhoon Ondoy was estimated at 17:00.


Final Report 3-19

Table 3.4 Peak Time of Past Measure Floods

Occurrence date

Peak Time Time lag of Sto.Nino and Rosario JS Montalban Sto.Nino Rosario JS

2000.11.3 10:00 13:00 14:00 1:00 2004.11.30 0:00 2:00 3:00 1:00 2009.9.26 - - 18:00 - 2011.9.27 15:00 18:00 19:00 1:00 2012.8.7 14:00 15:00 17:00 2:00



Figure 3.19 Hydrograph of 2000 Flood




Final Report 3-20








Final Report 3-21

3.2.3 Selection of Past Floods for Model Calibration and Verification

Out of 5 past floods for which hourly rainfall and water level data are available and the 5 highest water levels at Sto.Nino Station were recorded, the following 3 floods were selected for calibration and verification of the flood analysis model as the 3 largest basin daily rainfalls were recorded. Since the inundation area map is currently available only for Typhoon Ondoy as shown in Figure 3.25, data of Typhoon Ondoy was selected for calibration of model parameters.

For Calibration: Typhoon Ondoy in 2009 (Past Maximum)

For Verification: Flood on November 29-30, 2004 (Water level in Sto. Nino was the 4th highest after 1994)

For Verification: Flood on August 7-9, 2012 (Water level in Sto. Nino was the 2nd highest after 1994)

Table 3.5 Selection of Past Floods

Date Cause Peak WL at

Sto.Nino (EL.m)

Basin Rainfall at Sto.Nino (mm/1day)

(Probability) Apply Remarks

July 7, 2000 Typhoon 19.02 178.0 (1/10)

- 5th Highest WL at Sto.Nino after 1994

November 29, 2004 Typhoon 19.08 190.2 (1/10-1/20)

Veri

4th Highest WL at Sto.Nino after 1994

September 26, 2009 Typhoon Ondoy

Typhoon 22.16 290.8 (1/110)

Cali

Past Maximum

June 24, 2011 Monsoon 19.13 152.0 (1/5)

- 3rd Highest WL at Sto.Nino after 1994

August 7, 2012 Monsoon 20.42 271.7 (1/200)

Veri

2nd Highest WL at Sto.Nino after 1994

Remarks: Veri: for Verification, Cali: for Calibration Note: Probability of rainfall is different for typhoon type and monsoon type rainfalls. Source: JICA Study Team


Final Report 3-22

Source: Study of Water Security Master Plan for Metro Manila and its Adjoining Areas, JICA

Figure 3.24 Hydrograph of Past Measure Floods


Final Report 3-23


Figure 3.25 Observed Inundation Map for 2009 Flood


Final Report 3-24

3.2.4 Establishment of Flood Analysis Model

(1) Method of Model Calibration Model calibration was conducted as the following procedure.

Discharge to river course without inundation in upstream basin estimated by the runoff model (WEB-DHM) is given to the inundation model as a boundary condition.

Water level in river course and inundation area is estimated by the inundation model

Parameters are evaluated comparing estimated discharge, water level and inundation area to the observed ones.

The 2009 Flood (Typhoon Ondoy) was selected for calibration. As described below, the established model shows good reproductivity for relatively small peak flood such as the 2004 Flood and multi-peak flood such as 2012 Flood.

1) WEB-DHM Model Based on the parameters set by the “Study of Water Security Master Plan for Metro Manila and its Adjoining Areas”, surface soil parameters (ksat1, ksat2 and ksg) and roughness coefficient of river course were adjusted to reproduce short term runoff accurately.

2) Inundation Model Since the discharge at Sto.Nino Station varies depending on inundation volume upstream, the roughness coefficient which was set by the JICA Study was adjusted.

(2) Result of Model Calibration and Verification

1) Calibration by Typhoon Ondoy in 2009

<WEB-DHM Model>

The surface soil parameters and roughness coefficient were calibrated comparing the estimated discharge using the recalculated H-Q equation based on observed water level (hereinafter referred to as the “observed discharge”) and the calculated discharge. The output of WEB-DHM is discharge to river course without inundation upstream. Thus, the model was calibrated to meet hydrographs before inundation in upstream occurs, and inundation areas and hydrographs by the inundation model.


Figure 3.26 Observed and Calculated Hydrographs by WEB-DHM Model (2009 Flood at Sto.Nino)

Calculated hydrograph meets the observed hydrograph before inundation occurs.

Calculated hydrograph does not meet the observed one because inundation in upstream basin cannot be reproduced. However, hydrograph and peak discharge by the inundation analysis meet well.


Final Report 3-25

<Inundation Model>

The roughness coefficient was calibrated comparing the observed discharge and water level, and the calculated discharge and water level so that the model can reproduce the peak discharge and rising phase of flood accurately. The comparison of the observed and calculated hydrographs is shown in Figure 3.27. The simulated inundation map is shown in Figure 3.28. Besides, estimated peak discharge is shown in Figure 3.29.


Figure 3.27 Observed and Calculated Hydrographs by Inundation Model (2009 Flood)


Final Report 3-26




Final Report 3-27

4,540

3,200

3,940

800

3,580

3,750

1,140 780 760 1,390

720 2,370

400

Laguna LakeM

anga

han

Floo

dway

Nap

inda

n Ch

anne

lMarikina River (Lower)Pasig River

Nangka River

Rodriguez Bridge

Propsed Dem Site

Mar

ikin

a Ri

ver

Sto.Nino

Pasig River

San

Juan

Riv

er

Estimated DichangeTyphoon Ondoy(Sep 2009)

Manila Bay


Figure 3.29 Simulated Peak Discharge of 2009 Flood

2) Verification by Flood on November 29-30, 2004 The simulation results of floods on November 29-30, 2004 using the parameters calibrated by the 2009 Flood as shown as below.

<WEB-DHM Model> The comparison of the observed and calculated hydrographs is shown in Figure 3.30.


Figure 3.30 Observed and Calculated Hydrographs by WEB-DHM Model (2004 Flood)


Final Report 3-28

<Inundation Model>

The comparison of the observed and calculated hydrographs is shown in Figure 3.31. The simulated and inundation map is shown in Figure 3.32.




Final Report 3-29




Final Report 3-30

3) Verification by Flood on August 7-10, 2012

The simulation results of floods on August 7-10, 2012 using the parameters calibrated by the 2009 Flood as shown as below.

<WEB-DHM Model>

The comparison of the observed and calculated hydrographs is shown in Figure 3.33.


Figure 3.33 Observed and Calculated Hydrographs by WEB-DHM Model (2012 Flood)

<Inundation Model> The comparison of the observed and calculated hydrographs is shown in Figure 3.34. The simulated and inundation map is shown in Figure 3.35.


Final Report 3-31




Final Report 3-32




Final Report 3-33

(3) Evaluation of Analysis Results

By WEB-DHM which calculates discharge to river course as a boundary condition, calculated hydrograph does not meet the observed one. It is because WEB-DHM model calculates discharge before inundation occurs, and discharge inducing inundation as shown in Figure 3.36 cannot be reproduced since reduction of discharge by inundation is not calculated.

Since the calculated hydrographs by the WEB-DHM model meet the observed hydrographs before inundation occurs and hydrographs and peak discharges by the inundation analysis meet well, the runoff analysis results is evaluated as proper.

2009 2004 2012 Source: JICA Study Team

Figure 3.36 Inundation Simulation Results

As described above, the established model integrating the WEB-DHM model and the inundation model shows good reproductivity for the maximum past flood in 2009, relatively small peak flood such as the 2004 Flood and multi-peak flood such as 2012 Flood. Since the model shows good reproductivity for various types of floods, the established flood analysis model is evaluated as proper and utilized to estimate the basic design discharge and the design flood discharge.

<Inundation upstream of Sto.Nino> Inundation causes reduce of discharge and delay of peak occurrence time.


Final Report 4-1

CHAPTER 4 ANALYSIS OF DESIGN FLOOD DISCHARGE

4.1 Preconditions for Analysis As preconditions for analysis of design flood discharge, existing facilities, plans for the “Pasig-Marikina River Channel Improvement Project (Phase III)”, design water level in previous studies, current flow capacity, and proposed measures by the “Study on Flood Control and Drainage Project in Metro Manila” (hereinafter referred to as the “JICA M/P Study”) and “Master Plan for Flood Management in Metro Manila and Surrounding Areas” (hereinafter referred to as the “WB Study”) are confirmed as follows.

4.1.1 Existing Facilities

(1) Manggahan Floodway Manggahan Floodway was constructed in 1988 to protect the center of Metro Manila from 100 years probable flood with design discharge of 2,400m3/s.

Currently, the original flow capacity has been reduced mainly due to informal settler families in the course of floodway and sedimentation.

There are three tributaries to Manggahan Floodway named Cainta, Buli and Maho rivers. However, they will be diverted to East Manggahan Floodway which in under planning.

(2) Rosario Weir Rosario Weir was constructed in 1986 to control diversion between Manggahan Floodway and Pasig-Marikina River. Gate control is conducted to divert a part of flood discharge to Laguna Lake. On the other hand, gate control is also conducted to reduce the water level of Laguna Lake when it is higher than that of Marikina River to protect lakeshore area. It is also has another function to divide Pasig-Marikina Basin and Laguna Lake Basin which is originally different river basins for environmental conservation purpose.

Figure 4.1 Front View of Rosario Weir


Final Report 4-2

Figure 4.2 Operation Rule of Rosario Weir

4.1.2 Current Flow Capacity Current flow capacity of Pasig-Marikina is calculated with the conditions shown in Table 4.1. Result is shown in Table 4.2 and Figure 4.3. The average ratio of current flow capacities against design discharges are about 50% in Pasig, 80% in lower Marikina and 20% in upper and upper-upper Marikina. Flood control ratio is especially low in upper and upper-upper Marikina.

Table 4.1 Conditions for Flow Capacity Calculation Item Description

Calculation Method Non-uniform Flow Calculation River Section Current Condition as of 2010 with 100 interval Roughness Coefficient Pasig (-2.800ｋ～17.1k) :n=0.028

Lower Marikina (17.1k～23.700k) :n=0.028 Upper Marikina (23.700k～30.350k) :n=0.028 Upper Upper Marikina (30.350k～44.770k) :n=0.030

Lower End Start W.L. High Water Level 11.4（-2.800k） Calculation Case 0.1, 0.2, 0.4, 0.6, 0,8, 1.0, 1.2 and 1.4 times of 30 years probable flood Evaluated Elevations Dyke Crest, Land Elevation and HWL

Table 4.2 Results of Flow Capacity Calculation

River Name Stretch (Km)

Flow Capacity (m3/s) Design Discharge for

PMRCIP(m3/s) Present Condition

Average Minimum Maximum (1) Pasig River 0.0-1.0

1.0-4.0 4.0-7.0

7.0-17.1

1,200 600

1,000 500

900 200 600 200

1,500 1,200 1,500 1,000

1200

600 (2) Lower Marikina 0.0-6.5 400 200 1,000 550 (3) Upper Marikina 6.6-13.2 400 100 2900 以上 2900 (4)Upper Upper Marikina 13.2-27.62 500 50 2900 以上 -

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Final Report 4-7

4.1.3 Proposed Projects by Study on Flood Control and Drainage Project in Metro Manila

The proposed projects by the JICA M/P Study with the objective of 1/100 year probable flood are Markina Dam, MCGS and channel improvement works as summarized in Figure 4.7.

Source: The Study on Flood Control and Drainage Project in Metro Manila, JICA

Figure 4.7 Proposed Projects and Design Discharge Allocation by JICA M/P Study

(1) Pasig-Marikina Rivera. Channel Improvement

Design Discharge(m3/s)

Work ItemDesign

DischargeWork Item

Pasig 18,495 1,150 Dredging Same as Framework Plan500 Rehabilitation

Lower Marikina 6,790 500 - ditto - Same as Framework PlanUpper Marikina 20,565 2,900 Dredging Same as Framework Plan

DykeSan Juan 10,653 900 Dredging Same as Framework Plan

b. Strutcures

(5) Laguna LakeLength

(m)5,242

10,700

9,200

SectionLength

(m)

Framework Plan (100 years) Master Plan (100 years)

Strutcture Framework Plan (100 years) Master Plan (100 years)

Framework Plan

Same as Framework PlanSpan 137.6m x Width 5.4mSteel Plate Girder

Marikina Control Gate

(Reconstrutcion)Pandakan Bridge

Strutcture

Marikina DamStrutcture (MCGS)

Roller GateH 10.1m x W 17.5m x 2 unitsConcrete Gravity DamDam Height 70mOrifice Type Spillway

Same as Framework Plan

Same as Framework Plan

(Riveebed Width : 60 m)Dredging

Crest Level : 14.2 m)(Design WL : 12.5m

DykeCrest Level : 13.3m)

Panyarake Floodway

Lakeshore Dyke

Master Plan

ChannelImprovement of Napindan

Crest Level : 15.5 m)(Design WL : 13.8m

DykeCrest Level : 14.6m)(Design WL : 13.8m

DykeDredging

(Design WL : 12.5mDyke

Dredging

1,150 500 2,900

0

2,400

300

900

2,600 1,500 2,100

200

500MANILABAY

SAN JUANRIVER

NAPINDANRIVER

MANGAHANFLOODWAY

NANGKARIVER

MABIKLRADAN

MCCS

ROSARIOWEIR

SATO. NINO

PUMP

MONTALBAN

NHCS


Final Report 4-8

4.1.4 Pasig-Marikina River Channel Improvement Project (Phase III)

Design flood discharge allocation was reviewed in the Preparatory Study for Pasig-Marikina Channel Improvement Project (Phase III) (hereinafter referred to as the JICA Study) in connection with occurrence of Typhoon Ondoy in 2009. The project plan is abstracted as follows.

(1) Objective of Project

1) Objectives of Overall PMRCIP Project The objectives of the overall project are to mitigate the flood damage caused by channel overflow of the Pasig-Marikina River, to facilitate urban development, and to enhance the favorable environment along the river, as itemized below.

To mitigate the frequent inundation or massive flooding caused by the overflowing of Pasig-Marikina River resulting in severe damages to lives, livestock, properties and infrastructure with the aim of alleviating the living and sanitary conditions in Metro Manila including parts of Rizal Province;

To create a more dynamic economy by providing a flood-free urban center as an important strategy for furthering national development; and

To rehabilitate and enhance the environment and aesthetic view along the riverside areas by providing with more ecologically stable condition which will arrest the progressive deterioration of environmental conditions, health and sanitation in Metro Manila.

2) Objective of Phase III Project In the context of the objectives of the overall project, objective of the Phase III Project is to implement the river channel improvement project for the stretch of Lower Marikina River and the remaining portions of Pasig River which are not covered by the ongoing Phase II Project. (2) Design Flood Discharge The target area of Phase III Project is the priority area out of potential area in Pasig River and Lower Marikina River. Implementation plan is reviewed considering site conditions based on the detailed design conducted by DPWH in 2002 and its review in 2008.

As urgent flood countermeasure, channel improvement plan was formulated to increase flow capacity to meet 1/30 years flood as shown in Figure 4.8. Based on the condition that MCGS would be constructed in future, design flood discharges are 550m3/s in Lower Marikina River, 600m3/s in Upper Pasig River and 1,200m3/s in Lower Pasig River.

Source: Preparatory Study for Pasig-Marikina Channel Improvement Project (Phase III)

Figure 4.8 Design Flood Discharge Allocation for Phase III Project


Final Report 4-9

(3) Channel Improvement Plan in Pasig and Lower Marikina Rivers

1) Design High Water Level (DHWL) The applied design high water level for Pasig-Marikina River has been set through the detailed design stage (D/D) in 2002. Before the D/D, the structures provided in the Pasig-Marikina River Channel such as bridges, drainage facilities and navigation facilities were designed with reference to the ground height, recorded maximum flood level and so on around the site of each structure, leading to the provision of so many facilities and structures along the Pasig-Marikina River Channel.

In the detailed design stage, the Design High Water Level was set by mainly considering the following points:

To minimize the effect to existing river related structures (bridges, drainage facilities, port facilities and navigation facilities).

To minimize damage in case collapse of dike by minimizing the difference between the ground height and design high water level.

To keep the design high water level within the recorded maximum flood water.

To apply the average high spring tide at the design water level of river mouth, which is also the design height of port and coastal facilities.

2) Design Channel Alignment

Metro-Manila has been developed along the Pasig-Marikina river course since the ancient time where the area is fully utilized with houses, factories, commercial buildings and many infrastructures, so that the widening of river channel is almost impossible without drastically setting back the existing buildings or facilities. In this connection, the channel alignment follows the existing awkward river alignment, though it is desirable to modify the existing river alignment to smoothen the design alignment from the flooding point of view. Since this channel alignment set-up in the Detailed Design Stage seems to be the limit, it is assumed that this alignment will be maintained without any change in the future.

3) Design Longitudinal Profiles of Riverbed and DHWL

Pasig River, which is drains into Manila Bay, remarkably receives tidal influence and the flow capacity is not expected to increase so much by dredging and maintenance of the dredged river bed requires maintenance dredging time to time. From this consideration, the design longitudinal profile of riverbed for the Pasig River is based on the existing riverbed.

On the other hand, the riverbed of Lower Marikina River is required to be dredged for about 2m for navigation purpose and maintenance dredging also is required to assure the flow capacity of the Lower Marikina river channel.

4) Design Cross Sections Since Pasig River runs through the urbanized area of Metro Manila, single section is applied to minimize land acquisition and resettlement. As the results, the lower reach Pasig River of confluence of San Juan River is 100 m as minimum river width except meandering section while the river width of Upper Pasig is 60 m and more. For Lower Marikina River, minimum river width is 90m.

5) Design Freeboard

Freeboard is applied to the design of flood control structures corresponding to the design discharge in accordance with the “Design Guidelines, Criteria and Standard” of DPWH, as shown in Table 4.3. Since design discharge is more than 500m3/s in whole section, freeboard of 1.0m is applied.


Final Report 4-10

Table 4.3 Design Freeboard Design Discharge (m3/s) Freeboard (m)

Less than 200 0.6 200～500 0.8

500～2,000 1.0

6) Confirmation of Flow Capacity for Improved River Channel and Limit of River Channel Improvement

The flow capacity based on the design water level, dyke height, channel alignment, cross section and riverbed level which are set by above mentioned procedures was examined by non-uniform calculation and it was confirmed that the flow capacity corresponds to the design discharge distribution under a 30-year return period flood, if MCGS is constructed.

The design features for the river channel improvement expressed by the design high water level, alignment, longitudinal profile and cross-section is almost the limit for the Pasig-Marikina River and further improvement is difficult so that it will be difficult also to increase the flow capacity in a manner of river channel improvement. In this connection, it would be necessary to provide storage facilities in the upper river basin such as dam and retarding basin to store the excess discharge, and to further enhance the safety level as well as introduce nonstructural measures in the Pasig-Marikina River basin.

4.1.5 Proposed Projects by WB Study The Proposed projects by the WB Study is as summarized in Table 4.4 and Figure 4.11 consisting the improvement of Upper and Upper-Upper Marikina River, Marikina Large Dam, re-improvement of Pasig River and Lower Marikina River and improvement of San Juan River and Napindan Channel with design flood discharge of 1/100 years return period. In the WP Plan, the current diversion system using both Manggahan Floodway and Napindan Channel is applied without construction of MCGS, which is against the concept of PMRCIP. This plan has several critical issues such as large scale dredging in lower Pasig resulting high maintenance cost required, re-improvement works are required such as heightening of dykes and bridges in Lower Marikina and uncertainty of natural diversion from Pasig to Laguna Lake through NHCS.

In the planning, 4 alternative plans shown in Table 4.5 and Figure 4.12 and 4.13 were compared and the Alternative-2 was selected.

Table 4.4 Proposed Projects by WB Study Item Description

Target Year 2035 Design Scale 1/100 years

Components

1) Improvements of the Upper and Upper Upper Marikina River (upstream from bifurcation of Manggahan Floodway to the existing Wawa Dam)

2) Construction of Marikina Large Dam 3) Re-improvement of the Pasig River and Lower Marikina River and improvement of

the San Juan River and the Napindan Channel Project Cost 198,435 Mil. Pesos


Final Report 4-11


Figure 4.9 Proposed Projects by WB Study


Final Report 4-12

Table 4.5 Alternative Plans by WB Study

Alternatives

Item

Pasig Downstream*

Pasig Upstream**

Napindan Channel Lower Marikina Mangahan

Floodway Upper Marikina

Upper Upper Marikina Project

Cost (mil. Peso)

River mouth to the Confluence of San Juan R.

The confluence of San Juan R. to Napindan Channel

Napindan Gate to the Laguna Lake

The confluence of Napindan Channel to the Rosario Weir

Rosario Weir to the Laguna Lake

Rosario Weir to Marikina Bridge

Upstream from Marikina Bridge

Alt-0 RI & RTB

Exca.,River Widening(more than 130m in width), and Reconstruction of Dikes

Exca., River Widening (more than 130m in width), and Reconstruction of Dikes

Flood Wall Enhancement (Heightening: 1m to 30 cm)

River Widening (more than 120m) and Flood Wall (2m to 3m)

Exca. and Widening (more than 270m)

Exca., Flood Wall and Widening (more than 140m)

RTB and Excavation 444,041

Alt-1 RI,RTB, Small Dam

Exca. (Channel Width: 90m)

Existing Condition (Channel Width: 90m)


Flood Wall (0.8m to 2.4m)

Exca. (removal of sedimentation)

Dike and Exca. (Width: 90m)

RTB, Small Dam, Small Concrete Wall

202,094

Alt-2 RI, RTB, Large Dam




Flood Wall (0.8m to 2.0m)

Exca. (removal of sedimentation)


RTB, Large Dam, Small Concrete Wall

198,435

Alt-3 RI, RTB, Large Dam and MCGS




MCGS Exca. (removal of sedimentation)


RTB, Large Dam, Small Concrete Wall

208,776

RI: River improvement, RTB: Retarding Basin, MCGS: Marikina Control Gate Structure, Exca: Excavation *: River mouth to the Junction of San Juan and Pasig River, **: Upstream from the Junction, Small Dam: 47 MCM Gross Storage Volume, Large Dam: 75 MCM Gross Storage Volume Source: Master Plan for Flood Management in Metro Manila and Surrounding Areas, the World Bank


Figure 4.10 Alternatives for Design Flood Discharge Allocation


Final Report 4-13


Figure 4.11 Alternative Plans by WB Study

Large Marikina Dam Large Marikina Dam


Final Report 4-14

4.1.6 Comparison of Previous Studies

Analysis methods and plans for the JICA Study and the WB Study were compared as shown in Table 4.6

Table 4.6 Comparison of Previous Studies Preparatory Survey on Pasig-Marikina River Channel

Improvement Project (Phase III) (JICA) Master Plan for Flood Management in Metro

Manila and Surrounding Areas（WB） Design

Hyetograph Middle-peak Fictional Hyetograph

Hyetograph based on probable rainfall intensities by rainfall durations of Port Area

Type 1: Typhoon Ondoy Type Observed Hyetograph

Type 2: Middle-peak Fictional Hyetograph Hyetograph based on probable rainfall intensities by rainfall durations of Port Area

Estimation of Basin Average

Rainfall

Rainfall at Port Area x Rainfall Adjustment Coefficient Estimated as uniform rainfall in whole area

Type 1: Typhoon Ondoy Type Thiessen Method and Adjustment by IDW Method Estimated each 34 Thiessen Polygon

Type 2: Middle-peak Fictional Hyetograph IDW Method Estimated for 3 Sub-basins

Basin Average Probable Rainfall

Whole Basin (2 days) ・30 years 392.3mm ・100 years 445.8mm

Type 1: Typhoon Ondoy Type Observed 2 days rainfall x Enlargement Ratio Estimated each 34 Thiessen Polygon 3 Sub-basin Average Rainfall (Trial by WB Study)

ReturnPeriod

SB-01 SB-02 SB-3130 368 369 390

100 439 444 468

Probable 2 days Rainfall

Type 2: Middle-peak Fictional Hyetograph

Estimated for 3 Sub-basins ReturnPeriod

SB-01 SB-02 SB-3130 368 366 382

100 438 441 458


Probable

Discharge at St.Nino

Annual highest water level in 1958-77, 1086 and 1994-2009 are converted by H-Q Equations. H-Q Equations:

Q = 32.03 ×( H-10.80)2 H < 17.0 Q = 17.49 × (H-8.61)2 H > 17.0

Peack Discharge by Ondoy Typhoon (2009)

3,211m3/sec Probability Analysis of Annual Peak Discharge

30 Years: 2,750 m3/sec 100 Years: 3,390 m3 /sec

Probable Discharge in Previous Study 30 Years: 2,900 m3/sec 100 Years: 3,500 m3 /sec

Annual highest water level in 1958-77, 1086 and 1994-2009 are converted by H-Q Equations. H-Q Equations:

Q = 31.44 ×( H-10.96)2 H > 13.0 Peack Discharge by Ondoy Typhoon (2009)

3,950 m3/sec Probability Analysis of Annual Peak Discharge

(None)

Runoff Anlysis Rainfall-Runoff Model Storage Function Method: Mountanious Area Quasilinier Storage Type: Urbanized Area

Calibration and Verification of Model Parameters

2 fllods in 2004 was reproduced. Model parameters were calibrated to conform

calculated hydrograph to observed discharge. Parameters for Storage Function Method (delay

factors) were determined based on previous model.

Integrated Analysis Model of Basin, River and Flood Plains

Basin: Rainfall-Runoff Model (SCS Unit Hydrograph Method)

River: One-dimensional Unsteady Flow Model Flood Plain: Two-dimensional Unsteady Flow

Model

Calibration and Verification of Model Parameters Flood by Ondoy Typhoon was reproduced. Model parameters were calibrated to conform

calculated hydrograph to observed peak discharge and water level.

Model was verified by reproducing 2004 flood and 1998 flood.

Inundation Analysis

Inundation Alaysis Model River: One-dimensional Unsteady Flow Model Flood Plain: Two-dimensional Unsteady Flow

Integrated Analysis Model of Basin, River and Flood Plains

Flood by Ondoy Typhoon was reproduced.


Final Report 4-15

Preparatory Survey on Pasig-Marikina River Channel Improvement Project (Phase III) (JICA)

Master Plan for Flood Management in Metro Manila and Surrounding Areas（WB）

Model Flood by Ondoy Typhoon was reproduced. Simulation results were well conformed with

interview survey results. Flood management effects of River Chasnnel Improvement Project Phases II & III and Manggahan Floodway was examined.

Simulation results were well conformed with inundation map based on flood damage survey.

Runoff Calculation of

Design Rainfalls

Probable Discharge at Sto.Nino 30 Years: 2,740 m3/sec 100 Years: 3,210 m3/sec No overflow from river course was assumed.

Probable Discharge at Sto.Nino 30 Years: 3,600 m3/sec 100 Years: 4,100 m3/sec Overflow from river course was assumed. In the section between confluence of Nangka River

and Rosario Weir in Marikina River, large scale overflow and inundation due to dike break was assumed.

Design Discharge Allocation

Discharge Allocation of 100 Years Return Period Discharge with Only River Channel Improvement Works (Without MCGS)

Section Q(m3/s)

Wawa 1,890 Rodoriges Bridge 2,500 Before Nangka River 2,850 St. Nino 3,210 Mangahan Floodway 2,100 Lower Marikina River 1,130 Napindan Channel 0 Pasig River 1,155 San Juan River 770 Pasig River – Manila Bay 1,400

Based on flood runoff analysis, previous discharge

allocation was applied for Phase III Project Measures against 30 Years Flood: River Channel

Improvement & MSGS (Not to be implemented in Phase III Project)

Discharge Allocation of 30 Years Return Period Discharge (Without MCGS)

Section Q(m3/s)

Wawa 1,590 Rodoriges Bridge 2,110 Before Nangka River 2,420 St. Nino 2,740 Mangahan Floodway 1,820 Lower Marikina River 920 Napindan Channel 0 Pasig River 955 SanJuan River 690 Pasig River – Manila Bay 1,210

Discharge Allocation of 100 Years Return Period Discharge with Only River Channel Improvement Works (Alternative 0)

Section Q(m3/s)

Wawa 3,600 Montalban Bridge 4,800 (Retarding Basin) St. Nino 4,600 Mangahan Floodway 3,300 Lower Marikina River 1,500 Napindan Channel 1,100 Pasig River 850 San Juan River 1,800 Pasig River – Manila Bay 1,900

Alternative 2 consisting of the following measures

against 100 years return period flood was recommended.

- River Channel Improvement - Marikina Dam - Retarding Basins - Non-structural Measures

Discharge Allocation of 100 Years Return Period

Discharge (Alternative 2)

Section Q(m3/s) Wawa 3,600 Marikina Dam 900 Montalban Bridge 2,400 (Retarding Basin) St. Nino 2,900 Mangahan Floodway 2,000 Lower Marikina River 1,000 Napindan Channel 600 Pasig River 850 SanJuan River 1,000 Pasig River – Manila Bay 1,800



Final Report 4-16

4.2 Review of Rainfall Analysis

4.2.1 Results of Rainfall Analysis Conditions for calculation and its results as 30 years and 100 years return periods rainfall which obtained by the Study of Water Security Master Plan for Metro Manila and its Adjoining Areas (hereinafter referred to as the JICA Water Security Study) are summarized in Table 4.7, Table 4.9 to 4.11 and Figure 4.14 and 15 while the rainfall analysis results in the previous studies are shown in Table 4.8.

The JICA Water Security Study applied 1 day rainfall based on the analysis for correlation between rainfall duration and peak water level at Sto.Nino, while the previous studies applied 2 days rainfall.

Besides, the JICA Water Security Study applied several design hyetographs based on the observed hyetographs while the previous studies applied only milled-peak fictional hyetograph and the hyetograph of Typhoon Ondoy.

Table 4.7 Summary of Rainfall Analysis Item Description

Control Point Sto. Nino Duration of Design Rainfall

1 day (based on available data set and reasonableness of peak discharge occurrence)

Flood Concentration Time 11 hours (Method using Observation Data: 11 hours, Empirical Formula:7 hours)

Probable Rainfall 1/100: 285.5mm/1day (Typhoon type rainfall N=58, Gumbel Distribution) (1/30: 232.4mm/day) (Refer to Table 3.5)

Design Hyetographs

Enlarge of past actual hyetographs (7 hyetographs considering spatial variations) Fictional hyetograph (Middle-peak distribution without consideration of spatial variations) (Refer to Table 3.6, Table 3.7 and Figure 3.4)

Source: JICA Study Team based on Study of Water Security Master Plan for Metro Manila and its Adjoining Areas

Table 4.8 Comparison of Rainfall Analysis in Previous Studies Preparatory Survey on Pasig-Marikina River Channel

Improvement Project (Phase III) (JICA) Master Plan for Flood Management in Metro

Manila and Surrounding Areas（WB） Design

Hyetograph Middle-peak Fictional Hyetograph

Hyetograph based on probable rainfall intensities by rainfall durations of Port Area

Type 1: Typhoon Ondoy Type Observed Hyetograph

Type 2: Middle-peak Fictional Hyetograph Hyetograph based on probable rainfall intensities by rainfall durations of Port Area

Estimation of Basin Average

Rainfall

Rainfall at Port Area x Rainfall Adjustment Coefficient Estimated as uniform rainfall in whole area

Type 1: Typhoon Ondoy Type Thiessen Method and Adjustment by IDW Method Estimated each 34 Thiessen Polygon

Type 2: Middle-peak Fictional Hyetograph IDW Method Estimated for 3 Sub-basins

Basin Average Probable Rainfall

Whole Basin (2 days) ・30 years 392.3mm ・100 years 445.8mm

Type 1: Typhoon Ondoy Type Observed 2 days rainfall x Enlargement Ratio Estimated each 34 Thiessen Polygon 3 Sub-basin Average Rainfall (Trial by WB Study)

ReturnPeriod

SB-01 SB-02 SB-3130 368 369 390

100 439 444 468


Type 2: Middle-peak Fictional Hyetograph

Estimated for 3 Sub-basins ReturnPeriod

SB-01 SB-02 SB-3130 368 366 382

100 438 441 458



Final Report 4-17

Table 4.9 Results of Probable Rainfall Analysis

Items 1 day Rainfall 2 days Rainfall Case 1 Case 2 Case 3 JICA, 2011 WB, 2012 Case 4 JICA, 2011 WB, 2012

Meteor. Type T M All All All All All All Model Gumbel Gumbel Gumbel-

Chow Gumbel Gumbel Gumbel Gumbel-

Chow Gumbel

Sample Number 58 61 63 94 35 63 87 35 1/30 Rainfall 232.4 m 203.3 m 251.2 m 255.0 m 268 mm 410.1mm 392.3mm 367 mm

(Estimate Error) 20.1mm 16.3mm 17.4mm N/A N/A 31.3mm N/A N/A 1/100 Rainfall 285.5mm 244.6mm 303.6mm 286.5mm 344mm 494.8mm 445.8mm 439 mm

(Estimate Error) 26.1mm 21.2mm 22.4mm N/A N/A 40.9mm N/A N/A Selection

Selected Not Selected Not Selected - - Not Selected - -

N/A: Not Available, T: Tropical Depression, M: Monsoon and Others Source: Study of Water Security Master Plan for Metro Manila and its Adjoining Areas

Table 4.10 Cases of Design Hyetographs Enlarge of Actual Past Hyetograph Fictional hyetograph

Time Variation

Actual Hourly Rainfalls is enlarged. Middle-peak Distribution based on Hyetograph utilized in the Preparatory Survey on Pasig-Marikina River Channel Improvement Project (Phase III)

Spatial Variations

Spatial variations by Thiessen Distribution are applied.

None


Table 4.11 Design Hyetographs by Enlargement of Actual Past Hyetographs

No. Date Event

Probability Basin Mean Rainfall (1 Day)

Selection Observed 1/100 Rain fall Ratio Type Name (A) (B) (B/A)

1 2009/9/26 T Ondoy 1/110 290.8mm 285.5mm 0.982 Selected 2 2012/8/7 M - 1/200 271.7mm 244.6mm 0.900 Not Selected 3 1998/10/22 T Loleng 1/30 234.0mm 285.5mm 1.220 Selected 4 2004/11/29 T Winnie 1/10-1/20 190.2mm 285.5mm 1.501 Selected 5 2003/5/27 T Chedeng 1/10-1/20 189.4mm 285.5mm 1.507 Selected 6 2000/7/7 T Edeng 1/10 178.0mm 285.5mm 1.604 Selected 7 1997/8/18 M - 1/10 170.0mm 244.6mm 1.439 Not Selected 8 2002/7/7 M - 1/5-1/10 156.5mm 244.6mm 1.563 Not Selected 9 2011/6/24 T Falcon 1/5 152.0mm 285.5mm 1.878 Selected 10 2000/11/2 T Seniang 1/5 149.0mm 285.5mm 1.916 Selected

T:Tropical Depression, M:Monsoon and Others Remark: Typhoon type rainfall is applied considering conformity with probable rainfall. Source: Study of Water Security Master Plan for Metro Manila and its Adjoining Areas


Final Report 4-18

Station Status

Science Garden Out of Basin

Napindan No Data

Mt.Campana No Data

Aries Fully Av ailable

Nangka Fully Av ailable

BosoBoso Fully Av ailable

Mt.Oro Fully Av ailable

Station Status

Science Garden No Data

Napindan No Data

Mt.Campana No Data


Nangka Partly Av ailable

BosoBoso Partly Av ailable


Station Status


Napindan No Data

Mt.Campana No Data

Aries No Data

Nangka No Data



Station Status


Napindan Out of Basin

Mt.Campana Fully Av ailable





Station Status


Napindan Out of Basin

Mt.Campana Fully Av ailable





0.0

30.0

60.0

90.0

09/25 08:00 09/26 08:00 09/27 08:00 09/28 08:00

2009.9.26

DesignObserved

0.0

30.0

60.0

90.0

08/06 08:00 08/07 08:00 08/08 08:00 08/09 08:00

2012.8.7

DesignObserved

0.0

30.0

60.0

90.0

10/21 08:00 10/22 08:00 10/23 08:00 10/24 08:00

1998.10.22

DesignObserved

0.0

30.0

60.0

90.0

11/28 08:00 11/29 08:00 11/30 08:00 12/01 08:00

2004.11.29

DesignObserved

0.0

30.0

60.0

90.0

05/26 08:00 05/27 08:00 05/28 08:00 05/29 08:00

2003.5.27

DesignObserved


Figure 4.12 Design Hyetographs (1/100) (1/2)

Not Selected


Final Report 4-19

Station Status


Napindan No Data

Mt.Campana No Data

Aries No Data

Nangka No Data



Station Status


Napindan No Data

Mt.Campana No Data

Aries No Data

Nangka No Data



Station Status


Napindan No Data

Mt.Campana No Data

Aries No Data

Nangka No Data



Station Status


Napindan No Data

Mt.Campana No Data





Station Status


Napindan No Data

Mt.Campana No Data

Aries No Data

Nangka No Data



0.0

30.0

60.0

90.0

08/17 08:00 08/18 08:00 08/19 08:00 08/20 08:00

1997.8.18

DesignObserved

0.0

30.0

60.0

90.0

07/06 08:00 07/07 08:00 07/08 08:00 07/09 08:00

2002.7.7

DesignObserved

0.0

30.0

60.0

90.0

07/06 08:00 07/07 08:00 07/08 08:00 07/09 08:00

2000.7.7

DesignObserved

0.0

30.0

60.0

90.0

06/23 08:00 06/24 08:00 06/25 08:00 06/26 08:00

2011.6.24

DesignObserved

0.0

30.0

60.0

90.0

120.0

11/01 08:00 11/02 08:00 11/03 08:00 11/04 08:00

2000.11.2

DesignObserved

0.0

30.0

60.0

90.0

0 24 48 72

Model

Design


Figure 4.13 Design Hyetographs (1/100) (2/2)

Not Selected

Not Selected


Final Report 4-20

4.2.2 Design Rainfall Duration

The JICA Water Security Study reviewed the design rainfall duration in the previous studies and applied 1 day rainfall.

The previous studies applied 2 days rainfall to cover the observed rainfall durations of past floods. However, as shown in Figure 4.16, 1 day rainfall shows better correlation with peak water level comparing to the correlation between 2 days rainfall and peak discharge. Since the flood concentration time is estimated about 11 hours, it is not so effect to estimate flood discharge that the design rainfall duration does not cover the observed rainfall duration. Thus, the applied design rainfall duration by the JICA Water Security Study is considered as appropriate.


Figure 4.14 Correlation between Basin Average Rainfalls and Peak Discharge (Left: 1 day, Right: 2 days)

4.2.3 Basin Average Rainfall

In the JICA Water Security Study, spatial variation of rainfall is estimated by Thiessen method and IDW method for the observed hyetographs while it is not estimated for middle-peak fictional hyetograph since the unified rainfall intensity is estimated. For estimation of probable rainfall, simple average method is applied since there is no significant difference between simple average method and Thiessen method.

The methods applied in the previous studies are as follows.

JICA Study : Spatial variation is not considered since one middle-peak fictional hyetograph is based on the rainfall intensity of Port Area Station is applied.

WB Study : Spatial variation of rainfall is estimated by Thiessen method and IDW method for the hyetographs of Typhoon Ondoy and IDW method for middle-peak fictional hyetograph

Since observed data increase since 1994 resulting that runoff analysis based on observed hyetograph is available, the method applied by the JICA Water Security Study which can describe spatial and time variations of rainfall is considered as appropriate.

4.2.4 Basin Average Probable Rainfall According to the review of design rainfall duration, basin average probable rainfall is estimated in the JICA Water Security Study. Several probability distribution models are applied and the most suitable model is selected. And unbiased estimate value by Jackknife method is applied as probable hydrological value. It is considered that the method applied by the JICA Water Security Study which can describe spatial and time variations of rainfall is considered as appropriate.


Final Report 4-21

4.3 Basic Design Discharge

Based on the established flood analysis model, basic design discharge is estimated using the hyetographs described in Section 4.2.1. It is noted that probability 1 day rainfall of the hyetograph of Typhoon Ondoy is evaluated as 1/110 years, however, it is not cut down to meet the 1/100 years rainfall since the both values are almost same.

The flood analysis was conducted with the following conditions.

Water Level of Laguna Lake: 13.90 m (the highest water level after 1989)

Sea Level of Manila Bay: High Water Level 11.40 m (same as the previous studies)

Napindan Channel: 2 cases with open and closed

Natural Retarding Function Upstream: 2 cases with and without natural retarding function upstream of Sto.Nino and upper San Juan River Basin

Peak Discharge: The peak discharge at each point is applied as basic design discharge

4.3.1 Water Level of Laguna Lake

(1) Water Level of Laguna Lake in Previous Studies

As a boundary condition for non-uniform flow calculation and inundation analysis, water level of Laguna Lake was set in as shown in Table 4.12.

Table 4.12 Water Level of Laguna Lake in Previous Studies

Study Water Level of Laguna Lake

JICA M/P Study (1990)

・For Non-uniform Flow Calculation: 12.5 m (Average Annual Maximum Water Level) ・Inundation Analysis: 13.8 m (Adjusted based on the Past Highest Water Level)

JICA Study (2011) 12.2m (Average of Past Flood Event)

WB Study (2012) Observed Hydrograph of Typhoon Ondoy (12.78～13.85 m)

(2) Water Level of Laguna Lake in This Study For setting the design water level of Laguna Lake, relation of water levels at Sto.Nino Station (Marikina River) and Anggono Station (Laguna Lake) using the hourly water level data after 1994 is analyzed.

It is confirmed that water level of Laguna Lake rise when flood occurs in Marikina River of which water level at Sto.Nino becomes more than 18 m and flooding occurs.

However, there is no significant relation about peak time of water levels between Marikina River and Laguna Lake such the case that peak water levels occur at almost same time, the peak water level of Laguna Lake is recorded prior to or behind.

It is due to spatial and time variations of rainfall and there is a possibility that peak time of water levels between Marikina River and Laguna Lake such the case that peak water levels occur at same time.

Based on this examination results, the water levels applied in the previous studies are not appropriate as described as follows.

JICA Study: The average of past flood events of 12.2 m is applied which is less than the observed water level of Typhoon Ondoy. It is considered too low.

WB Study: Observed hydrograph of Typhoon Ondoy was applied which is a considerable case as a boundary


Final Report 4-22

condition of analysis. However, as the planning, higher water level shall be assumed due to the following reasons.

There are cases that peak water level occurs in Laguna Lake prior to Pasig-Marikina River.

Once water level rises in Laguna Lake, it takes time to start recession.

Water level of Laguna Lake effects to diversion discharge of Manggahan Floodway.

Therefore, the highest water level after 1989 when Manggahan Floodway constructed is applied in this Study. Annual highest water level in Laguna Lake is shown in Table 4.13.


WL_Max WL_Max(m) (m)

1989 12.24 2001 12.69 Mean annual highest water level (1989-2012)1990 12.67 2002 12.55 12.57m1991 12.60 2003 11.721992 12.39 2004 11.85 Mean annual highest water level (Major flood)1993 12.27 2005 12.15 13.54ｍ1994 12.27 2006 12.301995 12.94 2007 12.491996 12.52 2008 12.141997 11.83 2009 13.851998 12.70 2010 12.091999 13.47 2011 12.612000 13.53 2012 13.90

:Year of major flood occurrence

year year


(3) Water Level Rise in Laguna Lake due to Inflow from Pasig-Marikina River Main factor of water level rise of Laguna Lake is confirmed by calculating relation of inflow volume from Pasig-Marikina River and water level rise of Laguna Lake in the case of Typhoon Ondoy.

As a result of flood simulation, inflow volume from Pasig-Marikina River is estimated at 169 MCM consisting 115 MCM through Manggahan Floodway and 54 MCM through Napindan Channel. This inflow volume is equivalent to 0.18 m based on H-Q equation of Laguna Lake as shown in Figure 4.17, which is only 17% of total water level rise during the Typhoon Ondoy as shown in Figure 4.18.

Thus, it is judged that main factor of water level rise is rainfall in Laguna Basin and effect of diversion from Pasig-Marikina is very small.


Final Report 4-23

5.0

6.0

7.0

8.0

9.0

10.0

11.0

12.0

13.0

14.0

15.0

16.0

17.0

0 2,500,000,000 5,000,000,000 7,500,000,000 10,000,000,000

H (m

)

V (m3)

Laguna Lake's H-V

H-V 1997

H-V 2009


Figure 4.15 H-V Curve of Laguna Lake


Figure 4.16 Factors of Water Level Rise in Laguna Lake during Typhoon Ondoy

4.3.2 Basic Design Discharge The peak discharges of design hyetographs at Sto.Nino and their hydrographs are shown in Table 4.14 and Figure 4.21 to 28, respectively. The highest peak discharge is recorded at 2009/9/26 Flood (Typhoon Ondoy). Thus, basic design flood is determined applying 2009/9/26 hydrograph of which basic design discharge allocation is shown in Figure 4.19 and 4.20.

In case of “With Natural Retarding Function”, discharges are reduced comparing “Without Natural Retarding Function” with about 1,000 m3/s for 1/30 years flood and about 1,400 m3/s for 1/100 years flood.

Inundation upstream of Sto.Nino consists of inundation in natural retarding basin and inundation in upstream. This natural retarding basin is discussed in the flowing sections.


Final Report 4-24


Without Retarding With Retarding2009/9/26 4,980 3,575

1998/10/22 2,173 2,1502004/11/29 4,215 3,0122003/5/27 2,269 2,1492000/7/7 2,994 2,7812011/6/24 2,030 1,8132000/11/2 4,178 3,300

RIDF 2,825 2,530

Type Sto.Nino Qp


1/30 years with NHCS Open 1/100 years with NHCS Open

1/30 years with NHCS Closed 1/100 years with NHCS Closed


Figure 4.17 Basic Design Discharge Allocation (Without Natural Retarding Function)


Final Report 4-25

1/30 years with NHCS Open 1/100 years with NHCS Open

1/30 years with NHCS Closed 1/100 years with NHCS Closed


Figure 4.18 Basic Design Discharge Allocation (With Natural Retarding Function)


Final Report 4-26


Figure 4.19 Hyetograph and Hydrograph of 2009/9/26 Flood




Final Report 4-27






Final Report 4-28






Final Report 4-29




Figure 4.26 Hyetograph and Hydrograph of Middle-peak Fictional Flood